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Sample records for gallium alloys

  1. Optical microcharacterization of gallium nitride and indium gallium nitride alloys

    NASA Astrophysics Data System (ADS)

    Srinivasan, Sridhar

    Gallium Nitride (GaN) and its alloys are attractive candidate materials for light-emitting applications in the visible and ultraviolet regions of the electromagnetic spectrum. The wide direct bandgap of the III-nitrides makes them very efficient light-emitters and their short bond length makes them extremely robust and durable. During the last decade, there have been rapid strides in the development of these materials and several devices based on them have already been commercialized. However, there are many issues with these materials that remain to be solved. This dissertation focuses on two main issues: one, the properties of Indium Gallium Nitride (InGaN) and two, the effect of dislocations on material properties. InGaN alloys are very difficult to grow, and a principal effort in the research community today is to achieve growth of high-quality films with high indium compositions. In order to overcome the problems associated with the growth of InGaN, it is important to gain an understanding of the basic nature of the material. In this work, the microstructure and electronic properties of thick InGaN epilayers has been studied. This enables investigation of material properties free of quantum confinement effects. The electronic properties of InGaN were observed to strongly vary with indium composition. Dislocations in the underlying GaN layer act as nucleation sites for phase separation and have a significant effect on material properties. The dislocation density was also found to play an important role in determining the strain relaxation mechanism in InGaN epilayers. The effect of dislocations on materials properties is an interesting problem that is being studied in great detail. In this study, it was found that the electronic properties in epitaxial lateral overgrowth of GaN are strongly dependent on the growth direction and unrelated to dislocation density. The properties appeared to be determined by point defects whose incorporation depends on the growth surface. Luminescence characteristics were studied across threading dislocations in semi-insulating GaN and were found to be closely related to the electrostatic potential measured by electron holography. This work has investigated important materials issues in GaN and InGaN and has contributed in developing a basic understanding of these materials.

  2. Method for Plutonium-Gallium Separation by Anodic Dissolution of a Solid Plutonium-Gallium Alloy

    SciTech Connect

    Miller, William E.; Tomczuk, Zygmunt

    1998-12-08

    Purified plutonium and gallium are efficiently recovered from a solid plutonium-gallium (Pu-Ga) alloy by using an electrorefining process. The solid Pu-Ga alloy is the cell anode, preferably placed in a moving basket within the electrolyte. As the surface of the Pu-Ga anode is depleted in plutonium by the electrotransport of the plutonium to a cathode, the temperature of the electrolyte is sufficient to liquify the surface, preferably at about 500 C, resulting in a liquid anode layer substantially comprised of gallium. The gallium drips from the liquified surface and is collected below the anode within the electrochemical cell. The transported plutonium is collected on the cathode surface and is recovered.

  3. Thermodynamic properties of uranium in gallium-aluminium based alloys

    NASA Astrophysics Data System (ADS)

    Volkovich, V. A.; Maltsev, D. S.; Yamshchikov, L. F.; Chukin, A. V.; Smolenski, V. V.; Novoselova, A. V.; Osipenko, A. G.

    2015-10-01

    Activity, activity coefficients and solubility of uranium was determined in gallium-aluminium alloys containing 1.6 (eutectic), 5 and 20 wt.% aluminium. Additionally, activity of uranium was determined in aluminium and Ga-Al alloys containing 0.014-20 wt.% Al. Experiments were performed up to 1073 K. Intermetallic compounds formed in the alloys were characterized by X-ray diffraction. Partial and excess thermodynamic functions of U in the studied alloys were calculated.

  4. [Dimensional changes of silver and gallium-based alloy].

    PubMed

    Ballester, R Y; Markarian, R A; Loguercio, A D

    2001-01-01

    Gallium-based dental alloys were created with the aim of solving the problem of toxicity of mercury. The material shows mechanical properties similar to those of dental amalgam, but researches point out two unfavorable characteristics: great corrosion and excessive post-setting expansion, and the latter is capable of cracking dental structures. The aim of this study was to evaluate, during 7 days, the in vitro dimensional alteration of a gallium dental alloy (Galloy, SDI, Australia), in comparison with a dental amalgam containing zinc (F400, SDI, Australia), as a function of the contact with saline solution (0.9% NaCl) during the setting period. The storage experimental conditions were: storage in dry environment, immersion in saline solution and contamination during condensation. Additionally, the effects of contamination during the trituration of dental amalgam and the effects of protecting the surface of the gallium alloy with a fluid resin were studied. Specimens were stored at 37 degrees C +/- 1 degree C, and measuring was carried out, sequentially, every 24 h during 7 days. When the gallium alloy was either contaminated or immersed, an expansion significantly greater than that observed in the other experimental conditions was noticed after 7 days. The application of a fluid resin to protect the surface of the cylinders was able to avoid the increase in expansion caused by superficial moisture. The amalgam alloy did not show significant dimensional alterations, except when it was contaminated during trituration. PMID:11787323

  5. Microfluidic platforms for gallium-based liquid metal alloy

    NASA Astrophysics Data System (ADS)

    Kim, Daeyoung

    As an alternative to toxic mercury, non-toxic gallium-based liquid metal alloy has been gaining popularity due to its higher thermal and electrical conductivities, and low toxicity along with liquid property. However, it is difficult to handle as the alloy becomes readily oxidized in atmospheric air environment. This instant oxidation causes the gallium-based liquid metal alloy to wet almost any solid surface. Therefore, it has been primarily limited to applications which rely only on its deformability, not on its mobility. In this research, various approaches to mobilize gallium-based liquid metal alloy were investigated. Multi-scale surface patterned with polydimethylsiloxane (PDMS) micro pillar array showed super-lyophobic property against gallium-based liquid metal alloy by minimizing the contact area between the solid surface and the liquid metal, and it was expanded to a three-dimensional tunnel shaped microfluidic channel. Vertically-aligned carbon nanotube forest leads to another promising super-lyophobic surface due to its hierarchical micro/nano scale combined structures and chemical inertness. When the carbon nanotubes were transferred onto flexible PDMS by imprinting, the super-lyophobic property was still maintained even under the mechanical deformation such as stretching and bending. Alternatively, the gallium-based liquid metal can be manipulated by modifying the surface of liquid metal itself. With chemical reaction with HCl 'vapor', the oxidized surface (mainly Ga2O3/Ga2O) of gallium-based liquid metal was converted to GaCl3/InCl 3 resulting in the recovery of non-wetting characteristics. Paper which is intrinsically porous is attractive as a super-lyophobic surface and it was found that hydrochloric acid (HCl) impregnation enhanced the anti-wetting property by the chemical reaction. As another alternative method, by coating the viscoelastic oxidized surface of liquid metal with ferromagnetic materials (CoNiMnP or Fe), it showed non-wetting property and became moveable by applying a magnetic field. Finally, using its metallic and liquid properties, microfluidic-based applications of gallium-based liquid metal alloy such as inkjet printing and reconfigurable photomask were investigated. A clog-free and oxide-free inkjet printing technique was developed by incorporating HCl-impregnated paper as orifice. Inkjet-printed liquid metal line can be used as a metallic interconnect even with significant deformation of the flexible substrate. Additionally, based on its ultraviolet light blocking property, a reconfigurable photolithography using gallium-based liquid metal alloy was demonstrated in a PDMS-based 7-segments microfluidic channel by showing single digit numbers ('0'˜'9') with attainable minimum feature size of 10 microm.

  6. Bending of iron-gallium (Galfenol) alloys for sensor applications

    NASA Astrophysics Data System (ADS)

    Downey, Patrick R.; Flatau, Alison B.

    2006-03-01

    This project investigates the magnetomechanical sensing behavior of iron-gallium alloys in response to applied bending loads in order to provide an experimental and analytic framework for implementing this material in novel sensor applications at the nanoscale. A series of experiments are conducted on millimeter sized cantilevered beams to verify that the material is mechanically sound as well as magnetically active in this loading configuration, with results showing a change in magnetic induction of as much as 0.3 T occurring at twice the frequency of beam vibration. These results agree well with an analytic system model based on nonlinear free energy terms. Initial work has begun on visualizing and characterizing arrays of iron-gallium nanowires, with an atomic force microscope providing preliminary images as well as force and deflection data.

  7. Gallium

    SciTech Connect

    1996-01-01

    Discovered in 1875 through a study of its spectral properties, gallium was the first element to be uncovered following the publication of Mendeleev`s Periodic Table. French chemist, P.E. Lecoq de Boisbaudran, named his element discovery in honor of his native country; gallium is derived from the Latin word for France-{open_quotes}Gallia.{close_quotes}. This paper describes the properties, sources, and market for gallium.

  8. Electron backscatter diffraction of plutonium-gallium alloys

    SciTech Connect

    Boehlert, C. J.; Zocco, T. G.; Schulze, R. K.; Mitchell, J. N.; Pereyra, R. A.

    2002-01-01

    At Los Alamos National Laboratory a recent experimental technique has been developed to characterize reactive metals, including plutonium arid cerium, using electron backscatter diffraction (EBSD). Microstructural characterization of plutonium and its alloys by EBSD had been previously elusive primarily because of the extreme toxicity and rapid surface oxidation rate associated with plutonium metal. The experimental techniques, which included ion-sputtering the metal surface using a scanning auger microprobe (SAM) followed by vacuum transfer of the sample from the SAM to the scanning electron microscope (SEM), used to obtain electron backscatter diffraction Kikuchi patterns (EBSPs) and orientation maps for plutonium-gallium alloys are described and the initial microstructural observations based on the analysis are discussed. Combining the SEM and EBSD observations, the phase transformation behavior between the {delta} and {var_epsilon} structures was explained. This demonstrated sample preparation and characterization technique is expected to be a powerful means to further understand phase transformation behavior, orientation relationships, and texlure in the complicated plutonium alloy systems.

  9. Thermodynamic properties of uranium in liquid gallium, indium and their alloys

    NASA Astrophysics Data System (ADS)

    Volkovich, V. A.; Maltsev, D. S.; Yamshchikov, L. F.; Osipenko, A. G.

    2015-09-01

    Activity, activity coefficients and solubility of uranium was determined in gallium, indium and gallium-indium alloys containing 21.8 (eutectic), 40 and 70 wt.% In. Activity was measured at 573-1073 K employing the electromotive force method, and solubility between room temperature (or the alloy melting point) and 1073 K employing direct physical measurements. Activity coefficients were obtained from the difference of experimentally determined temperature dependencies of uranium activity and solubility. Intermetallic compounds formed in the respective alloys were characterized using X-ray diffraction. Partial and excess thermodynamic functions of uranium in the studied alloys were calculated. Liquidus lines in U-Ga and U-In phase diagrams from the side rich in gallium or indium are proposed.

  10. Application of iron-gallium alloy as magnetostrictive sensors

    NASA Astrophysics Data System (ADS)

    Datta, Supratik; Flatau, Alison B.

    2005-05-01

    There has been a growing need to develop non-contact sensors for use in real time structural health monitoring. Iron-Gallium alloys (Galfenol, Fe1-xGax, 0.13< x <0.21) appear to be a promising magnetostrictive material for such applications. This work discusses the concepts and methods used in developing a prototype Galfenol sensor for detecting bending induced strains and forces. The proof of concept experiment consists of two Galfenol patches attached on the top and bottom surfaces of an aluminum cantilevered beam. A solenoid applies a biasing magnetic field to the Galfenol patches. The change in Galfenol patch magnetic induction produced by compressive and tensile stresses during bending are continuously measured by a field sensor. The strains on the beam surface and Galfenol sensor surface are also measured using strain gages. The effect of biasing field at constant loading and the effect of loading at constant biasing field on the magnetic induction response have been investigated. A linear magneto-mechanical model for estimating the magnetic induction response for a given mechanical loading is presented.

  11. Galvanic corrosion and cytotoxic effects of amalgam and gallium alloys coupled to titanium.

    PubMed

    Bumgardner, J D; Johansson, B I

    1996-06-01

    The aim of this study was to examine and compare the galvanic corrosion of a conventional, a dispersed high-copper, and a palladium-enriched spherical high-copper amalgam and a gallium alloy coupled to titanium in saline and cell culture solutions, and to evaluate the effects of the couples on cultured cells. The potentials and charge transfers between amalgams and titanium were measured by electrochemical corrosion methods. Cytotoxicity of the couples, as indicated by the uptake of neutral red vital stain, was determined in 24-h direct contact human gingival fibroblast cell cultures. Results of this study indicated that before connecting the high-copper amalgams to titanium, the amalgams exhibited more positive potentials which resulted in initial negative charge transfers, i.e. corrosion of titanium. However, this initial corrosion appeared to cause titanium to passivate, and a shift in galvanic currents to positive charge transfers, i.e. corrosion of the amalgam samples. Lower galvanic currents were measured for the amalgam-titanium couples as compared to the gallium alloy-titanium couple. Coupling the conventional or the palladium-enriched high-copper amalgams to titanium did not significantly affect the uptake of neutral red as compared to cells not exposed to any test alloy. However, significant cytotoxic effects were observed when the dispersed-type high-copper amalgam and the gallium alloy were coupled to titanium. Even though the corrosion currents measured for these couples were less than gold alloys coupled to amalgam, these results suggest there is the potential for released galvanic corrosion products to become cytotoxic. These data warrant further investigations into the effects of coupling amalgam and gallium alloys to titanium in the oral environment. PMID:8831065

  12. Anodic polarization behavior and microstructure of a gallium-based alloy.

    PubMed

    Oshida, Y; Moore, B K

    1993-07-01

    A gallium-based alloy (GA) that was developed as a substitute for dental amalgam was investigated for anodic polarization behavior in deoxygenated Ringers solution, 37 degrees C. The related microstructures were examined and microanalyses were conducted. Four polarization tests were conducted by scanning from -300mV to +1,000 mV (vs. SCE) at 2 mV/s. Polarization of the first sample (GA-1) was stopped after the first anodic dissolution peak (-100 mV, 1.5-2.0 x 10(-3) A/cm2). The fourth sample (GA-4) was interrupted at the secondary peak (+1000 mV, 0.3 A/cm2). It was found that (1) the early stage of the first peak is related to selective dissolution of divalent tin ions, followed by a dissolution of Ga. Transmission electron diffraction (TED) identified the brown corrosion product as Ga2O3; (2) the GA-4 sample was covered with the white corrosion product of mainly Sn+4, identified as SnO2. In addition, the current density of the GA sample when coupled with a high-copper dental amalgam was 0.03 A/cm2 (with +1,000 mV) at the second peak which was about a ten times lower value than for the uncoupled sample; (3) the uncoupled gallium alloy and gallium alloy coupled with a high-copper dental amalgam showed 10(3)-10(4) times higher anodic current density than that of an uncoupled high-copper dental amalgam, suggesting that the gallium alloy is more corrosion prone. PMID:7988754

  13. Liquid-phase gallium-indium alloy electronics with microcontact printing.

    PubMed

    Tabatabai, Arya; Fassler, Andrew; Usiak, Claire; Majidi, Carmel

    2013-05-21

    Liquid-phase electronic circuits are patterned on an elastomer substrate with a microcontact printer. The printer head dips into a pool of a liquid-phase gallium-indium alloy, e.g., eutectic gallium-indium (EGaIn) or gallium-indium-tin (Galinstan), and deposits a single drop on a silicone elastomer substrate. After patterned deposition, the liquid-phase circuit is sealed with an additional layer of silicone elastomer. We also demonstrate patterned deposition of the liquid-phase GaIn alloy with a molded polydimethylsiloxane stamp that is manually inked and pressed into an elastomer substrate. As with other liquid-phase electronics produced through needle injection or masked deposition, the circuit is elastically deformable and can be stretched to several times its natural length without losing electronic functionality. In contrast to existing fabrication techniques, microcontact printing and stamp lithography can be used to produce circuits with any planar geometric feature, including electrodes with large planar area, intersecting and closed-loop wires, and combs with multiple terminal electrodes. In air, the surface of the coalesced droplets oxidize to form a thin oxide skin that preserves the shape of the circuit during sealing. This first demonstration of soft-lithography fabrication with liquid-phase GaIn alloy expands the space of allowable circuit geometries and eliminates the need for mold or mask fabrication. PMID:23659455

  14. Gallium suboxide vapor attack on chromium, cobalt, molybdenum, tungsten and their alloys at 1200 [degrees] C

    SciTech Connect

    Kolman, D. G.; Taylor, T. N.; Park, Y.; Stan, M.; Butt, D. P.; Maggiore, C. J.; Tesmer, Joseph R.; Havrilla, G. J.

    2004-01-01

    Our prior work elucidated the failure mechanism of furnace materi als (304 SS, 316 SS, and Hastelloy C-276) exposed to gallium suboxide (Ga{sub 2}O) and/or gallium oxide (Ga{sub 2}O{sub 3}) during plutonium - gallium compound processing. Failure was hypothesized to result from concurrent alloy oxidation/Ga compound reduction followed by Ga uptake. The aim of the current work is to screen candidate replacement materials. Alloys Haynes 25 (49 Co - 20 Cr - 15 W - 10 Ni - 3 Fe - 2 Mn - 0.4 Si, wt%), 52 Mo - 48 Re (wt%), 62 W - 38 Cu (wt%), and commercially pure Cr, Co, Mo, W, and alumina were examined. Preliminary assessments of commercially pure W and Mo - Re suggest that these materials may be suitable for furnace construction. Thermodynamics calculations indicating that materials containing Al, Cr, Mn, Si, and V would be susceptible to oxidation in the presence of Ga{sub 2}O were validated by experimental results. In contrast to that reported previously, an alternate reaction mechanism for Ga uptake, which does not require concurrent alloy oxidation, controls Ga uptake for certain materials. A correlation between Ga solubility and uptake was noted.

  15. Determination of lattice orientation in aluminium alloy grains by low energy gallium ion-channelling

    NASA Astrophysics Data System (ADS)

    Silk, Jonathan R.; Dashwood, Richard J.; Chater, Richard J.

    2010-06-01

    Polished sections of a fine-grained aluminium, silicon carbide metal matrix composite (MMC) alloy were prepared by sputtering using a low energy gallium ion source and column (FIB). The MMC had been processed by high temperature extrusion. Images of the polished surface were recorded using the ion-induced secondary electron emission. The metal matrix grains were distinguished by gallium ion-channelling contrast from the silicon carbide component. The variation of the contrast from the aluminium grains with tilt angle can be recorded and used to determine lattice orientation with the contrast from the silicon carbide (SiC) component as a reference. This method is rapid and suits site-specific investigations where classical methods of sample preparation fail.

  16. Frequency-Switchable Metamaterial Absorber Injecting Eutectic Gallium-Indium (EGaIn) Liquid Metal Alloy

    PubMed Central

    Ling, Kenyu; Kim, Hyung Ki; Yoo, Minyeong; Lim, Sungjoon

    2015-01-01

    In this study, we demonstrated a new class of frequency-switchable metamaterial absorber in the X-band. Eutectic gallium-indium (EGaIn), a liquid metal alloy, was injected in a microfluidic channel engraved on polymethyl methacrylate (PMMA) to achieve frequency switching. Numerical simulation and experimental results are presented for two cases: when the microfluidic channels are empty, and when they are filled with liquid metal. To evaluate the performance of the fabricated absorber prototype, it is tested with a rectangular waveguide. The resonant frequency was successfully switched from 10.96 GHz to 10.61 GHz after injecting liquid metal while maintaining absorptivity higher than 98%. PMID:26561815

  17. Czochralski growth of gallium indium antimonide alloy crystals

    SciTech Connect

    Tsaur, S.C.

    1998-02-01

    Attempts were made to grow alloy crystals of Ga{sub 1{minus}x}In{sub x}Sb by the conventional Czochralski process. A transparent furnace was used, with hydrogen purging through the chamber during crystal growth. Single crystal seeds up to about 2 to 5 mole% InSb were grown from seeds of 1 to 2 mole% InSb, which were grown from essentially pure GaSb seeds of the [111] direction. Single crystals were grown with InSb rising from about 2 to 6 mole% at the seed ends to about 14 to 23 mole% InSb at the finish ends. A floating-crucible technique that had been effective in reducing segregation in doped crystals, was used to reduce segregation in Czochralski growth of alloy crystals of Ga{sub 1{minus}x}In{sub x}Sb. Crystals close to the targeted composition of 1 mole% InSb were grown. However, difficulties were encountered in reaching higher targeted InSb concentrations. Crystals about 2 mole% were grown when 4 mole% was targeted. It was observed that mixing occurred between the melts rendering the compositions of the melts; and, hence, the resultant crystal unpredictable. The higher density of the growth melt than that of the replenishing melt could have triggered thermosolutal convection to cause such mixing. It was also observed that the floating crucible stuck to the outer crucible when the liquidus temperature of the replenishing melt was significantly higher than that of the growth melt. The homogeneous Ga{sub 1{minus}x}In{sub x}Sb single crystals were grown successfully by a pressure-differential technique. By separating a quartz tube into an upper chamber for crystal growth and a lower chamber for replenishing. The melts were connected by a capillary tube to suppress mixing between them. A constant pressure differential was maintained between the chambers to keep the growth melt up in the growth chamber. The method was first tested with a low temperature alloy Bi{sub 1{minus}x}Sb{sub x}. Single crystals of Ga{sub 1{minus}x}In{sub x}Sb were grown with uniform compositions up to nearly 5 mole% InSb.

  18. Measured iron-gallium alloy tensile properties under magnetic fields

    NASA Astrophysics Data System (ADS)

    Yoo, Jin-Hyeong; Flatau, Alison B.

    2004-07-01

    Tension testing is used to identify Galfenol material properties under low level DC magnetic bias fields. Dog bone shaped specimens of single crystal Fe100-xGax, where 17<=x<=33, underwent tensile testing along two crystalographic axis orientations, [110] and [100]. The material properties being investigated and calculated from measured quantities are: Young's modulus and Poisson's ratio. Data are presented that demonstrate the dependence of these material properties on applied magnetic field levels and provide a preliminary assessment of the trends in material properties for performance under varied operating conditions. The elastic properties of Fe-Ga alloys were observed to be increasingly anisotropic with rising Ga content for the stoichiometries examined. The largest elastic anisotropies were manifested in [110] Poisson's ratios of as low as -0.63 in one specimen. This negative Poisson's ratio creates a significant in-plane auxetic behavior that could be exploited in applications that capitalize on unique area effects produced under uniaxial loading.

  19. Alloying and Structure of Ultrathin Gallium Films on the (111) and (110) Surfaces of Palladium

    PubMed Central

    2013-01-01

    Growth, thermal stability, and structure of ultrathin gallium films on Pd(111) and Pd(110) are investigated by low-energy ion scattering and low-energy electron diffraction. Common to both surface orientations are growth of disordered Ga films at coverages of a few monolayers (T = 150 K), onset of alloy formation at low temperatures (T ≈ 200 K), and formation of a metastable, mostly disordered 1:1 surface alloy at temperatures around 400–500 K. At higher temperatures a Ga surface fraction of ∼0.3 is slightly stabilized on Pd(111), which we suggest to be related to the formation of Pd2Ga bulk-like films. While on Pd(110) only a Pd-up/Ga-down buckled surface was observed, an inversion of buckling was observed on Pd(111) upon heating. Similarities and differences to the related Zn/Pd system are discussed. PMID:24089625

  20. The microstructural, mechanical, and fracture properties of austenitic stainless steel alloyed with gallium

    NASA Astrophysics Data System (ADS)

    Kolman, D. G.; Bingert, J. F.; Field, R. D.

    2004-11-01

    The mechanical and fracture properties of austenitic stainless steels (SSs) alloyed with gallium require assessment in order to determine the likelihood of premature storage-container failure following Ga uptake. AISI 304 L SS was cast with 1, 3, 6, 9, and 12 wt pct Ga. Increased Ga concentration promoted duplex microstructure formation with the ferritic phase having a nearly identical composition to the austenitic phase. Room-temperature tests indicated that small additions of Ga (less than 3 wt pct) were beneficial to the mechanical behavior of 304 L SS but that 12 wt pct Ga resulted in a 95 pct loss in ductility. Small additions of Ga are beneficial to the cracking resistance of stainless steel. Elastic-plastic fracture mechanics analysis indicated that 3 wt pct Ga alloys showed the greatest resistance to crack initiation and propagation as measured by fatigue crack growth rate, fracture toughness, and tearing modulus. The 12 wt pct Ga alloys were least resistant to crack initiation and propagation and these alloys primarily failed by transgranular cleavage. It is hypothesized that Ga metal embrittlement is partially responsible for increased embrittlement.

  1. Magnetostriction and corrosion studies in single crystals of iron-gallium alloys

    NASA Astrophysics Data System (ADS)

    Jayaraman, Tanjore V.

    Iron-gallium alloys have an excellent combination of large low-field magnetostriction, good mechanical properties, low hysteresis, and relatively low cost. This dissertation focuses on the magneto striction and corrosion behaviors of single crystals of Fe-Ga alloys. In the first part, the variation of magnetostrictive coefficient: (3/2) lambda100, with composition and heat treatment conditions of Fe-Ga alloys, is examined. Single crystals with compositions Fe-15 at.% Ga, Fe-20 at.% Ga, and Fe-27.5 at.% Ga were obtained by (a) vertical Bridgman technique (DG) and (b) vertical Bridgman technique followed by long-term annealing (LTA) and quenching. Rapid quenching from a phase region improves the (3/2) lambda 100 value in these alloys. X-ray diffraction characterization showed for the first time the direct evidence of short-range ordering in these alloys. The second part reports the first study of alpha" ordering heat treatment on the elastic properties and magnetostriction of Fe-27.5 at.% Ga alloy single crystals. The elastic constants were measured using resonant ultrasound spectroscopy (RUS), and the elastic properties and magneto-elastic coupling constant were calculated. The (3/2) lambda100 and B1 values obtained for a phase were higher than alpha" phase. The third part examines the first study of corrosion behavior of as-cast FeGa and Fe-Ga-Al alloys in acidic, basic, and simulated seawater environments. Corrosion measurements were performed by Tafel scan and polarization resistance method and in general exhibited good corrosion resistance. The fourth part examines the first study of corrosion behavior of Fe-15 at.% Ga, Fe-20 at.% Ga, and Fe-27.5 at.% Ga DG and LTA alloy single crystals and the dependence of corrosion rates on the crystal orientations. The corrosion resistance was better in basic environments followed by simulated seawater and acidic environments. The fifth part examines the effect of magnetostriction on the corrosion behavior of [100]-oriented single crystal of Fe-20 at.% Ga alloy in acidic and simulated seawater solution, first study ever of this kind. Magnetostrictive strain introduced on the application of saturation magnetic field increased the corrosion rate of [100]-oriented Fe-20 at.% Ga alloy single crystal by 40% in 0.1M HCl and decreased the corrosion rate by 15% in 3.5 wt.% NaCl solution.

  2. Effect of microtextured surface topography on the wetting behavior of eutectic gallium-indium alloys.

    PubMed

    Kramer, Rebecca K; Boley, J William; Stone, Howard A; Weaver, James C; Wood, Robert J

    2014-01-21

    Liquid-embedded elastomer electronics have recently attracted much attention as key elements of highly deformable and "soft" electromechanical systems. Many of these fluid-elastomer composites utilize liquid metal alloys because of their high conductivities and inherent compliance. Understanding how these alloys interface with surfaces of various composition and texture is critical to the development of parallel processing technology, which is needed to create more complex and low-cost systems. In this work, we explore the wetting behaviors between droplets of gallium-indium alloys and thin metal films, with an emphasis on tin and indium substrates. We find that metallic droplets reactively wet thin metal foils, but the wettability of the foils may be tuned by the surface texture (produced by sputtering). The effects of both composition and texture of the substrate on wetting dynamics are quantified by measuring contact angle and droplet contact diameter as a function of time. Finally, we apply the Cassie-Baxter model to the sputtered and native substrates to gain insight into the behavior of liquid metals and the role of the oxide formation during interfacial processes. PMID:24358994

  3. Direct Band Gap Gallium Antimony Phosphide (GaSbxP1−x) Alloys

    PubMed Central

    Russell, H. B.; Andriotis, A. N.; Menon, M.; Jasinski, J. B.; Martinez-Garcia, A.; Sunkara, M. K.

    2016-01-01

    Here, we report direct band gap transition for Gallium Phosphide (GaP) when alloyed with just 1–2 at% antimony (Sb) utilizing both density functional theory based computations and experiments. First principles density functional theory calculations of GaSbxP1−x alloys in a 216 atom supercell configuration indicate that an indirect to direct band gap transition occurs at x = 0.0092 or higher Sb incorporation into GaSbxP1−x. Furthermore, these calculations indicate band edge straddling of the hydrogen evolution and oxygen evolution reactions for compositions ranging from x = 0.0092 Sb up to at least x = 0.065 Sb making it a candidate for use in a Schottky type photoelectrochemical water splitting device. GaSbxP1−x nanowires were synthesized by reactive transport utilizing a microwave plasma discharge with average compositions ranging from x = 0.06 to x = 0.12 Sb and direct band gaps between 2.21 eV and 1.33 eV. Photoelectrochemical experiments show that the material is photoactive with p-type conductivity. This study brings attention to a relatively uninvestigated, tunable band gap semiconductor system with tremendous potential in many fields. PMID:26860470

  4. Direct Band Gap Gallium Antimony Phosphide (GaSbxP1-x) Alloys

    NASA Astrophysics Data System (ADS)

    Russell, H. B.; Andriotis, A. N.; Menon, M.; Jasinski, J. B.; Martinez-Garcia, A.; Sunkara, M. K.

    2016-02-01

    Here, we report direct band gap transition for Gallium Phosphide (GaP) when alloyed with just 1-2 at% antimony (Sb) utilizing both density functional theory based computations and experiments. First principles density functional theory calculations of GaSbxP1-x alloys in a 216 atom supercell configuration indicate that an indirect to direct band gap transition occurs at x = 0.0092 or higher Sb incorporation into GaSbxP1-x. Furthermore, these calculations indicate band edge straddling of the hydrogen evolution and oxygen evolution reactions for compositions ranging from x = 0.0092 Sb up to at least x = 0.065 Sb making it a candidate for use in a Schottky type photoelectrochemical water splitting device. GaSbxP1-x nanowires were synthesized by reactive transport utilizing a microwave plasma discharge with average compositions ranging from x = 0.06 to x = 0.12 Sb and direct band gaps between 2.21 eV and 1.33 eV. Photoelectrochemical experiments show that the material is photoactive with p-type conductivity. This study brings attention to a relatively uninvestigated, tunable band gap semiconductor system with tremendous potential in many fields.

  5. Direct Band Gap Gallium Antimony Phosphide (GaSbxP1-x) Alloys.

    PubMed

    Russell, H B; Andriotis, A N; Menon, M; Jasinski, J B; Martinez-Garcia, A; Sunkara, M K

    2016-01-01

    Here, we report direct band gap transition for Gallium Phosphide (GaP) when alloyed with just 1-2 at% antimony (Sb) utilizing both density functional theory based computations and experiments. First principles density functional theory calculations of GaSbxP1-x alloys in a 216 atom supercell configuration indicate that an indirect to direct band gap transition occurs at x = 0.0092 or higher Sb incorporation into GaSbxP1-x. Furthermore, these calculations indicate band edge straddling of the hydrogen evolution and oxygen evolution reactions for compositions ranging from x = 0.0092 Sb up to at least x = 0.065 Sb making it a candidate for use in a Schottky type photoelectrochemical water splitting device. GaSbxP1-x nanowires were synthesized by reactive transport utilizing a microwave plasma discharge with average compositions ranging from x = 0.06 to x = 0.12 Sb and direct band gaps between 2.21 eV and 1.33 eV. Photoelectrochemical experiments show that the material is photoactive with p-type conductivity. This study brings attention to a relatively uninvestigated, tunable band gap semiconductor system with tremendous potential in many fields. PMID:26860470

  6. Shear strain mediated magneto-electric effects in composites of piezoelectric lanthanum gallium silicate or tantalate and ferromagnetic alloys

    SciTech Connect

    Sreenivasulu, G.; Piskulich, E.; Srinivasan, G.; Qu, P.; Qu, Hongwei; Petrov, V. M.; Fetisov, Y. K.; Nosov, A. P.

    2014-07-21

    Shear strain mediated magneto-electric (ME) coupling is studied in composites of piezoelectric Y-cut lanthanum gallium silicate (LGS) or tantalate (LGT) and ferromagnetic Fe-Co-V alloys. It is shown that extensional strain does not result in ME effects in these layered composites. Under shear strain generated by an ac and dc bias magnetic fields along the length and width of the sample, respectively, strong ME coupling is measured at low-frequencies and at mechanical resonance. A model is discussed for the ME effects. These composites of Y-cut piezoelectrics and ferromagnetic alloys are of importance for shear strain based magnetic field sensors.

  7. Colloidal gallium indium oxide nanocrystals: a multifunctional light-emitting phosphor broadly tunable by alloy composition.

    PubMed

    Farvid, Shokouh S; Wang, Ting; Radovanovic, Pavle V

    2011-05-01

    We demonstrate compositionally tunable photoluminescence in complex transparent conducting oxide nanocrystals. Alloyed gallium indium oxide (GIO) nanocrystals with variable crystal structures are prepared by a colloidal method throughout the full composition range and studied by different structural and spectroscopic methods, including photoluminescence and X-ray absorption. The structures and sizes of the GIO nanocrystals can be simultaneously controlled, owing to the difference in the growth kinetics of In(2)O(3) and Ga(2)O(3) nanocrystals and the polymorphic nature of both materials. Using the synthesized nanocrystal series, we demonstrate the structural and compositional dependences of the photoluminescence of GIO nanocrystals. These dependences, induced by the interactions between specific defect sites acting as electron donors and acceptors, are used to achieve broad emission tunability in the visible spectral range at room temperature. The nature of the photoluminescence is identified as donor-acceptor pair recombination and changes with increasing indium content owing to the changes in the energy states of, and interactions between, donors and acceptors. Structural analysis of GIO nanocrystals by extended X-ray absorption fine structure spectroscopy reveals that In(3+) occupies only octahedral, rather than tetrahedral, sites in the spinel-type γ-Ga(2)O(3) nanocrystal host lattice, until reaching the substitutional incorporation limit of ca. 25%. The emission decay dynamics is also strongly influenced by the nanocrystal structure and composition. The oxygen vacancy defects, responsible for the observed photoluminescence properties, are also implicated in other functional properties, particularly conductivity, enabling the application of colloidal GIO nanocrystals as integrated optoelectronic materials. PMID:21476551

  8. Characterization of bending magnetostriction in iron-gallium alloys for nanowire sensor applications

    NASA Astrophysics Data System (ADS)

    Downey, Patrick Ramon

    This research explores the possibility of using electrochemically deposited nanowires of magnetostrictive iron-gallium (Galfenol) to mimic the sensing capabilities of biological cilia. Sensor design calls for incorporating Galfenol nanowires cantilevered from a membrane and attached to a conventional magnetic field sensor. As the wires deflect in response to acoustic, air flow, or tactile excitation, the resultant bending stresses induce changes in magnetization that due to the scale of the nanowires offer the potential for excellent spatial resolution and frequency bandwidth. In order to determine the suitability for using Galfenol nanowires in this role, the first task was experimentally characterizing magnetostrictive transduction in bending beam structures, as this means of operation has been unattainable in previous materials research due to low tensile strengths in conventional alloys such as Terfenol-D. Results show that there is an appreciable sensing response from cantilevered Galfenol beams and that this phenomenon can be accurately modeled with an energy based formulation. For progressing experiments to the nanowire scale, a nanomanipulation instrument was designed and constructed that interfaces within a scanning electron microscope and allows for real time characterization of individual wires with diameters near 100 nm. The results of mechanical tensile testing and dynamic resonance identification reveal that the Galfenol nanowires behave similarly to the bulk material with the exception of a large increase in ultimate tensile strength. The magnetic domain structure of the nanowires was theoretically predicted and verified with magnetic force microscopy. An experimental methodology was developed to observe the coupling between bending stress and magnetization that is critical for accurate sensing, and the key results indicate that specific structural modifications need to be made to reduce the anisotropy in the nanowires in order to improve the transduction capabilities. A solution to this problem is presented and final experiments are performed.

  9. Gallium scan

    MedlinePlus

    Liver gallium scan; Bony gallium scan ... You will get a radioactive material called gallium injected into your vein. The gallium travels through the bloodstream and collects in the bones and certain organs. Your health care provider will ...

  10. Chemical short range order and magnetic correction in liquid manganese-gallium zero alloy

    NASA Astrophysics Data System (ADS)

    Grosdidier, B.; Ben Abdellah, A.; Osman, S. M.; Ataati, J.; Gasser, J. G.

    2015-12-01

    The Mn66Ga34 alloy at this particular composition is known to be zero alloy in which the linear combination of the two neutron scattering lengths weighted by the atomic compositions vanish. Thus for this specific concentration, the effect of the partial structure factors SNN and SNC is cancelled by a weighted term, which value is zero. Then the measured total structure factor S(q) gives directly the concentration-concentration structure factor SCC(q). We present here the first experimental results of neutron diffraction on the Mn66Ga34 "null matrix alloy" at 1050 °C. The main peak of the experimental SCC(q) gives a strong evidence of a hetero-atomic chemical order in this coordinated alloy. This order also appears in real space radial distribution function which is calculated by the Fourier transform of the structure factor. The degree of hetero-coordination is discussed together with other manganese-polyvalent alloys. However manganese also shows abnormal magnetic scattering in the alloy structure factor which must be corrected. This correction gives an experimental information on the mean effective spin of manganese in this liquid alloy. We present the first critical theoretical calculations of the magnetic correction factor in Mn-Ga zero-alloy based on our accurate experimental measurements of SCC(q).

  11. Thermodynamics of reaction of praseodymium with gallium-indium eutectic alloy

    NASA Astrophysics Data System (ADS)

    Melchakov, S. Yu.; Ivanov, V. A.; Yamshchikov, L. F.; Volkovich, V. A.; Osipenko, A. G.; Kormilitsyn, M. V.

    2013-06-01

    Thermodynamic properties of Ga-In eutectic alloys saturated with praseodymium were determined for the first time employing the electromotive force method. The equilibrium potentials of the Pr-In alloys saturated with praseodymium (8.7-12.1 mol.% Pr) and Pr-Ga-In alloys (containing 0.0012-6.71 mol.% Pr) were measured between 573-1073 K. Pr-In alloy containing solid PrIn3 with known thermodynamic properties was used as the reference electrode when measuring the potentials of ternary Pr-In-Ga alloys. Activity, partial and excessive thermodynamic functions of praseodymium in alloys with indium and Ga-In eutectic were calculated. Activity (a), activity coefficients (γ) and solubility (X) of praseodymium in the studied temperature range can be expressed by the following equations: lgaα-Pr(In) = 4.425 - 11965/T ± 0.026. lgаα-Pr(Ga-In) = 5.866 - 14766/T ± 0.190. lgγα-Pr(Ga-In) = 2.351 - 9996/T ± 0.39. lgХPr(Ga-In) = 3.515 - 4770/T ± 0.20.

  12. Effect of hydrogen and magnetic field on the mechanical behavior of magnetostrictive iron-gallium alloys

    NASA Astrophysics Data System (ADS)

    Ramanathan, Meenakshisundaram

    Magnetostrictive Fe-Ga and other iron-based alloys are candidates for use in sensing, actuation and large-scale energy harvesting applications. Exposure to aqueous electrochemical environments is anticipated in some of these applications which could potentially introduce hydrogen into the alloy and cause severe ductility reduction due to hydrogen embrittlement. These alloys may also be simultaneously exposed to magnetic field. This study therefore examines the effect of hydrogen and magnetic field on the mechanical behavior of these alloys. This study could also provide an understanding of the relationship between hydrogen embrittlement and magnetoelastic behavior in these alloys. In this work, the effect of hydrogen and magnetic field on the fracture behavior of [100]-oriented Fe-17.5 at.% Ga alloy single crystals and polycrystalline Fe-15 at.% Ga alloy were examined. Three-point bend tests and tensile tests were used to study the fracture behavior. Tests were done in different conditions to understand the effect of hydrogen and magnetic field on the fracture behavior of these materials. Hydrogen loading was done by in-situ electrochemical charging and magnetic field was applied to the samples either by using Nd2Fe 14B permanent magnets or by using solenoid coils. Before doing the three-point bend test on the Fe-Ga single crystal samples, tests were done using high-strength AISI 4340 steel to optimize the testing procedures and parameters. In all cases, the samples tested with hydrogen charging show a drastic reduction in ductility and fracture stress values. In the case of [100]-oriented Fe-17.5 at.% Ga alloy single crystal samples tested with hydrogen charging, the presence of applied magnetic field increased the stress required for fracture and a corresponding increase in bending strain values. This is attributed to a decrease of the elastic modulus values on the application of magnetic field in this magnetostrictive alloy. The hydrogen embrittlement was characterized by a change in fracture surface from a ductile type fracture to a brittle cleavage type fracture. Acoustic emission signals collected during the test correspond to the fracture behavior.

  13. Hort-Range Wetting at Liquid Gallium-Bismuth Alloy Surfaces: X-ray Measurements and Square-Gradient Theory

    SciTech Connect

    Huber, P.; Shpyrko, O; Pershan, P; Ocko, B; DiMasi, E; Deutsch, M

    2009-01-01

    We present an x-ray reflectivity study of wetting at the free surface of the binary liquid metal alloy gallium-bismuth (Ga-Bi) in the region where the bulk phase separates into Bi-rich and Ga-rich liquid phases. The measurements reveal the evolution of the microscopic structure of the wetting films of the Bi-rich, low-surface-tension phase along several paths in the bulk phase diagram. The wetting of the Ga-rich bulk's surface by a Bi-rich wetting film, the thickness of which is limited by gravity to only 50 Angstroms, creates a Ga-rich/Bi-rich liquid/liquid interface close enough to the free surface to allow its detailed study by x rays. The structure of the interface is determined with Angstromsngstrem resolution, which allows the application of a mean-field square gradient model extended by the inclusion of capillary waves as the dominant thermal fluctuations. The sole free parameter of the gradient model, the influence parameter K, that characterizes the influence of concentration gradients on the interfacial excess energy, is determined from our measurements. This, in turn, allows a calculation of the liquid/liquid interfacial tension, and a separation of the intrinsic and capillary wave contributions to the interfacial structure. In spite of expected deviations from MF behavior, based on the upper critical dimensionality (Du = 3 ) of the bulk, we find that the capillary wave excitations only marginally affect the short-range complete wetting behavior. A critical wetting transition that is sensitive to thermal fluctuations appears to be absent in this binary liquid-metal alloy.

  14. Surface preparation of gallium antimonide and indium antimonide for MBE growth and development of antimony alloy based devices

    NASA Astrophysics Data System (ADS)

    Vangala, Shivashankar

    Chemical mechanical polished Gallium Antimonide (GaSb) and Indium Antimonide (InSb) substrate surfaces are evaluated for molecular beam epitaxial (MBE) growth. Initialization of epitaxial growth is found to be vendor specific on GaSb (100) substrates due to vendor bulk material growth and polishing procedures. A novel surface processing method using Br-GLIB (gas cluster ion beam) is developed for producing "epiready" GaSb substrates and is tested for its applicability in MBE. Also, several new InSb chemical mechanical polishing techniques are evaluated by growing and characterizing MBE grown epitaxial layers on the substrates. Atomic hydrogen cleaning of GaSb and InSb surfaces suggested that surface processing under vacuum just before MBE growth may be required to optimize the growth process. Several novel MBE growth schemes are implemented to grow high quality AlGaAsSb epilayers with several Al compositions that closely lattice match to GaSb substrates. AlGaAsSb p-n junction diode structures are then grown and fabricated using novel passivating schemes. The dark currents are found to be less in the MBE grown AlGaAsSb p-n diodes as compared to diodes grown by liquid phase epitaxy (LPE). For the first time, the Silvaco ATLASTm device modeling scheme is used to study the internal and external characteristics of Sb alloy based devices using the latest data available for the impact ionization coefficients. Simulated results are in close agreement with experimental values for the p-n diodes as well as p-i-n diodes fabricated from material from another laboratory.

  15. Measurement of field-dependence elastic modulus of iron-gallium alloy using tensile test

    NASA Astrophysics Data System (ADS)

    Yoo, Jin-Hyeong; Flatau, Alison B.

    2005-05-01

    An experimental approach is used to identify Galfenol material properties under dc magnetic bias fields. Dog-bone-shaped specimens of single crystal Fe100-xGax, where 18.6⩽x⩽33.2, underwent tensile testing along two crystallographic axis orientations, [110] and [100]. Young's modulus and Poisson's ratio sensitivity to magnetic fields and stoichiometry are investigated. Data are presented that demonstrate the dependence of these properties on applied magnetic-field levels and provide a substantial assessment of the trends in material properties for performance of alloys of different stoichiometries under varied operating conditions.

  16. Measurement of field-dependence elastic modulus of iron-gallium alloy using tensile test

    SciTech Connect

    Yoo, Jin-Hyeong; Flatau, Alison B.

    2005-05-15

    An experimental approach is used to identify Galfenol material properties under dc magnetic bias fields. Dog-bone-shaped specimens of single crystal Fe{sub 100-x}Ga{sub x}, where 18.6{<=}x{<=}33.2, underwent tensile testing along two crystallographic axis orientations, [110] and [100]. Young's modulus and Poisson's ratio sensitivity to magnetic fields and stoichiometry are investigated. Data are presented that demonstrate the dependence of these properties on applied magnetic-field levels and provide a substantial assessment of the trends in material properties for performance of alloys of different stoichiometries under varied operating conditions.

  17. Metal organic chemical vapor deposition of indium gallium nitride alloys on nanowire substrates

    NASA Astrophysics Data System (ADS)

    Pendyala, Chandrashekhar

    Rising environmental concerns due to our rising population and energy demand along with our excessive dependence on fossil fuels has created an urgent need to find clean, renewable and carbon free source of energy. Photoelectrochemical (PEC) water splitting is a clean and carbon free process where hydrogen is produced from water and sunlight using a semiconductor. To date, no material has been found that meets the stringent requirements of band gap, band edge positions and stability for spontaneous water splitting. It is however possible to use two materials to meet the criteria. In this regard, InGaN alloys with indium rich composition are interesting materials. However, very little is understood about the synthesis of thick (˜200--300 nm), single crystal InGaN layers for PEC applications. Heteroepitaxial growth of InGaN films on planar substrates induces phase segregation due to stress. Here, we proposed to investigate the role of nanowires as strain relaxing substrates to mitigate phase segregation. GaN nanowires with controlled orientation and small diameters were synthesized on various substrates by controlling the temperature and material flux to control the nuclei formation. The mechanism to control the growth mode using equilibrium solubility was validated with the III-Sb system. InGaN layers with controlled composition were synthesized on the GaN nanowires in a custom built MOCVD reactor. The InGaN layers are single crystalline, without any phase segregation. It was observed that only nanowires with diameters < 30 nm led to the observation while nanowires with larger diameters (˜ 100 nm) act as planar substrates resulting in polycrystalline growth. The heteroepitaxial growth was observed to evolve from initial InGaN islands coalescing into single crystalline shell on the GaN nanowires. Morphology of the InGaN shells was observed to depend on the orientation of the GaN nanowire substrates with c-GaN nanowires resulting in hexagonal shell while a-GaN nanowires had rectangular shell. We also investigated a novel material system GaSbN using theoretical techniques for its applicability toward PEC water splitting. The electronic structure of GaSbN system with dilute antimony was investigated using theoretical simulations. Results indicate that only very small antimony content (< 10%) is required to achieve the right band gap. Most importantly, the band edges of GaSbN alloy seem to straddle the water splitting potentials that makes it a potential direct water splitting material.

  18. Evaluation of magnetostrictive shunt damper performance using Iron (Fe)-Gallium (Ga) alloy

    NASA Astrophysics Data System (ADS)

    Yoo, JinHyeong; Murray, Andrew; Flatau, Alison B.

    2014-04-01

    This study presents the possibility of dissipating mechanical energy with a proof-of-concept prototype magnetostrictive based shunt circuit using passive electrical components. The device consists of a polycrystalline galfenol (Fe-Ga alloy) strip bonded to a brass cantilever beam. Two brass pieces, each containing a permanent magnet, are used to mass load each end of the beam and to provide a magnetic bias field through the galfenol strip. The voltage induced in an induction coil closely wound around the cantilever beam captures the time rate of change of magnetic flux within the galfenol strip as the beam vibrates. The first bending-mode resonant frequency of the device was 69.42 Hz. To dissipate the electrical voltage from the device, a shunt circuit is attached. The effective mechanical impedance for the magnetostrictive shunt circuit is derived. The shunted model is specialized for two shunt circuits: the case of a resistor and that of a capacitance. The experimental results for both the resistive and capacitance shunt circuits validate the shunted magnetostrictive damping model for couple of cased of resistance and capacitance.

  19. Bending behavior of iron-gallium (Galfenol) alloys for sensor applications

    NASA Astrophysics Data System (ADS)

    Downey, Patrick R.; Flatau, Alison B.

    2005-05-01

    Galfenol alloys (Fe100-x Gax) have been shown to combine significant magnetostriction (~400 ppm) with strong mechanical properties (tensile strengths ~500 MPa), making them well suited for use in robust actuators and sensors as an active structural material. This project investigates the magnetomechanical bending behavior of Galfenol to facilitate the design concepts for using Galfenol in a variety of novel sensor applications. To this end, a series of experiments are conducted on the magnetic response of cantilevered beams to dynamic bending loads. The samples studied include polycrystalline Fe81.6Ga18.4 and Fe80.5Ga19.5 (1/8" diameter x 2" long) and single crystal Fe84Ga16 and Fe79Ga21 (1/16" diameter x 1" long). Mechanical excitation was applied to the tip of each rod, with tests performed with sinusoidal and broadband random inputs. Measuring the magnetic response of the samples were a giant magnetoresistive (GMR) sensor located behind the beam and a pickup coil wound directly on each rod. A combination of permanent magnets and solenoid provided dc fields to magnetically bias the samples. Results of initial testing show that sinusoidal bending produces measurable output in which the GMR sensor agrees well with the pickup coil, and that the output increases when subjected to increased magnetic bias. Random input tests confirm that the various system resonances can be detected from the frequency spectra. Other results examine the effects of composition, crystal structure, and z-axis position of the GMR sensor. The system is modeled by incorporating classical continuum mechanics, the constitutive magnetostriction equations, and nonlinear magnetization terms, the results of which are compared with the experiments.

  20. Surface reconstructions and morphology of indium gallium arsenide compound semiconductor alloys

    NASA Astrophysics Data System (ADS)

    Riposan, Alexandru

    Lattice-matched In0.53Ga0.47As/InP(001) and compressively strained In0.27Ga0.73As/GaAs(001) and In0.81Ga 0.19As/InP(001) compound semiconductor layers were grown by molecular beam epitaxy (MBE) and analyzed by in-situ scanning tunneling microscopy (STM) and ex-situ atomic force microscopy (AFM). Regular (4x3) and irregular (nx3) alloy reconstructions were observed at all compositions. In addition, the strained surfaces contain alpha2(2x4) and beta2(2x4) reconstructions at the lower and higher In compositions, respectively. New models were proposed for the (4x3) reconstruction, which are consistent with the experimental results and obey the electron counting rule. In these models, the (4x3) reconstruction is As-rich, but contains As-metal heterodimers, in addition to As dimers and metal dimers. These models can also be used to compose disordered (nx3) surfaces while still obeying the electron counting rule. The experiments suggest that the (2x4) reconstructions are favored by compressive misfit strain and are enriched in In compared with the (4x3)/(nx3) reconstructions. At moderate misfit strains and temperatures, the critical film thickness for three-dimensional (3D) growth is increased by increasing the As overpressure during film deposition. This effect provides an additional method to control the transition to 3D growth and has applications in device fabrication. Large 3D islands form during the annealing of planar pseudomorphic In 0.27Ga0.73As/GaAs films, and later disappear with continuing annealing. These islands are different from those formed during film deposition. The formation of these features is strain-driven, while their dissolution is triggered by In desorption. A step instability was also observed during annealing at this composition, consisting in the cusping of step edges and the formation of surface pits and step bunches. The driving force for this instability is likely the creation of new step line due to the compressive strain, through step undulation due to the large step separation. The nucleation of 3D pits during the growth of In0.27Ga 0.73As/GaAs compressively strained films is a localized phenomenon, occurring only in the proximity of 3D islands and at small island separation. The nucleation of pits in these regions was attributed to a reduced critical pit size, as a result of the overlapping strain fields of 3D islands and a reduced adatom density between islands.

  1. Gallium Safety in the Laboratory

    SciTech Connect

    Cadwallader, L.C.

    2003-05-07

    A university laboratory experiment for the US Department of Energy magnetic fusion research program required a simulant for liquid lithium. The simulant choices were narrowed to liquid gallium and galinstan (Ga-In-Sn) alloy. Safety information on liquid gallium and galinstan were compiled, and the choice was made to use galinstan. A laboratory safety walkthrough was performed in the fall of 2002 to support the galinstan experiment. The experiment has been operating successfully since early 2002.

  2. Gallium Safety in the Laboratory

    SciTech Connect

    Lee C. Cadwallader

    2003-06-01

    A university laboratory experiment for the US Department of Energy magnetic fusion research program required a simulant for liquid lithium. The simulant choices were narrowed to liquid gallium and galinstan (Ga-In-Sn) alloy. Safety information on liquid gallium and galinstan were compiled, and the choice was made to use galinstan. A laboratory safety walkthrough was performed in the fall of 2002 to support the galinstan experiment. The experiment has been operating successfully since early 2002.

  3. Gallium--A smart metal

    USGS Publications Warehouse

    Foley, Nora; Jaskula, Brian

    2013-01-01

    Gallium is a soft, silvery metallic element with an atomic number of 31 and the chemical symbol Ga. The French chemist Paul-Emile Lecoq de Boisbaudran discovered gallium in sphalerite (a zinc-sulfide mineral) in 1875 using spectroscopy. He named the element "gallia" after his native land of France (formerly Gaul; in Latin, Gallia). The existence of gallium had been predicted in 1871 by Dmitri Mendeleev, the Russian chemist who published the first periodic table of the elements. Mendeleev noted a gap in his table and named the missing element "eka-aluminum" because he determined that its location was one place away from aluminum in the table. Mendeleev thought that the missing element (gallium) would be very much like aluminum in its chemical properties, and he was right. Solid gallium has a low melting temperature (~29 degrees Celsius, or °C) and an unusually high boiling point (~2,204 °C). Because of these properties, the earliest uses of gallium were in high-temperature thermometers and in designing metal alloys that melt easily. The development of a gallium-based direct band-gap semiconductor in the 1960s led to what is now one of the most well-known applications for gallium-based products--the manufacture of smartphones and data-centric networks.

  4. Development of gallium aluminum phosphide electroluminescent diodes

    NASA Technical Reports Server (NTRS)

    Chicotka, R. J.; Lorenz, M. R.; Nethercot, A. H.; Pettit, G. D.

    1972-01-01

    Work done on the development of gallium aluminum phosphide alloys for electroluminescent light sources is described. The preparation of this wide band gap semiconductor alloy, its physical properties (particularly the band structure, the electrical characteristics, and the light emitting properties) and work done on the fabrication of diode structures from these alloys are broadly covered.

  5. Gallium complexes and solvent extraction of gallium

    SciTech Connect

    Coleman, J.P.; Graham, C.R.; Monzyk, B.F.

    1988-05-03

    This patent describes a process for recovering gallium from aqueous solutions containing gallium which comprises contacting such a solution with an organic solvent containing at least 2% by weight of a water-insoluble N-organo hydroxamic acid having at least about 8 carbon atoms to extract gallium, and separating the gallium loaded organic solvent phase from the aqueous phase.

  6. Gallium trace on-line preconcentration/separation and determination using a polyurethane foam mini-column and flame atomic absorption spectrometry. Application in aluminum alloys, natural waters and urine.

    PubMed

    Anthemidis, Aristidis N; Zachariadis, George A; Stratis, John A

    2003-07-27

    A sensitive and selective flow injection time-based method for on-line preconcentration/separation and determination of gallium by flame atomic absorption spectrometry at trace levels was developed. The on-line formed gallium chloride complex is sorbed onto a polyether-type polyurethane foam mini-column, followed by on-line quantitative elution with isobutyl methyl ketone and direct introduction into the flame pneumatic nebulizer of the atomic absorption spectrometer. All chemical and flow variables of the system as well as the possible interferences were studied. The manner of strong HCl solutions propulsion was investigated and established using a combination of two displacement bottles. For 90 s preconcentration time, a sample frequency of 28 h(-1), an enhancement factor of 40, a detection limit of 6 microg l(-1) and a precision expressed as relative standard deviation (s(r)) of 3.3% (at 1.00 mg l(-1)) were achieved. The calibration curve is linear over the concentration range 0.02-3.00 mg l(-1). The accuracy of the developed method was sufficient and evaluated by the analysis of a silicon-aluminum alloy standard reference material. Finally, it was successfully applied to gallium determination in commercial aluminum alloys, natural waters and urine. PMID:18969117

  7. Compositional control of the mixed anion alloys in gallium-free InAs/InAsSb superlattice materials for infrared sensing

    NASA Astrophysics Data System (ADS)

    Haugan, H. J.; Szmulowicz, F.; Mahalingam, K.; Brown, G. J.; Bowers, S. L.; Peoples, J. A.

    2015-08-01

    Gallium (Ga)-free InAs/InAsSb superlattices (SLs) are being actively explored for infrared detector applications due to the long minority carrier lifetimes observed in this material system. However, compositional and dimensional changes through antimony (Sb) segregation during InAsSb growth can significantly alter the detector properties from the original design. At the same time, precise compositional control of this mixed-anion alloy system is the most challenging aspect of Ga-free SL growth. In this study, the authors establish epitaxial conditions that can minimize Sb surface segregation during growth in order to achieve high-quality InAs/InAsSb SL materials. A nominal SL structure of 77 InAs/35 InAs0.7Sb0.3 that is tailored for an approximately six-micron response at 150 K was used to optimize the epitaxial parameters. Since the growth of mixed-anion alloys is complicated by the potential reaction of As2 with Sb surfaces, the authors varied the deposition temperature (Tg) under a variety of Asx flux conditions in order to control the As2 surface reaction on a Sb surface. Experimental results reveal that, with the increase of Tg from 395 to 440 C, Sb-mole fraction x in InAs1-xSbx layers is reduced by 21 %, under high As flux condition and only by 14 %, under low As flux condition. Hence, the Sb incorporation efficiency is extremely sensitive to minor variations in epitaxial conditions. Since a change in the designed compositions and effective layer widths related to Sb segregation disrupts the strain balance and can significantly impact the long-wavelength threshold and carrier lifetime, further epitaxial studies are needed in order to advance the state-of-the-art of this material system.

  8. Bismuth in gallium arsenide: Structural and electronic properties of GaAs1-xBix alloys

    NASA Astrophysics Data System (ADS)

    Reshak, Ali Hussain; Kamarudin, H.; Auluck, S.; Kityk, I. V.

    2012-02-01

    The structural and electronic properties of cubic GaAs1-xBix alloys with bismuth concentration 0.0, 0.25, 0.50, 0.75 and 1.0 are studied using the ‘special quasi-random structures' (SQS) approach of Zunger along with the generalized gradient approximation (GGA) and the Engel-Vosko generalized gradient approximation (EV-GGA). The lattice constant, bulk modulus, derivative of bulk modulus and energy gap vary with bismuth concentration nonlinearly. The present calculations show that the band gap decreases substantially with increasing bismuth concentration and that spin-orbit coupling influences the nature of bonding at high Bi concentrations.

  9. Bismuth in gallium arsenide: Structural and electronic properties of GaAs{sub 1-x}Bi{sub x} alloys

    SciTech Connect

    Reshak, Ali Hussain; Kityk, I.V.

    2012-02-15

    The structural and electronic properties of cubic GaAs{sub 1-x}Bi{sub x} alloys with bismuth concentration 0.0, 0.25, 0.50, 0.75 and 1.0 are studied using the 'special quasi-random structures' (SQS) approach of Zunger along with the generalized gradient approximation (GGA) and the Engel-Vosko generalized gradient approximation (EV-GGA). The lattice constant, bulk modulus, derivative of bulk modulus and energy gap vary with bismuth concentration nonlinearly. The present calculations show that the band gap decreases substantially with increasing bismuth concentration and that spin-orbit coupling influences the nature of bonding at high Bi concentrations. - Graphical abstract: Bowing effect of spin-orbit split-off band values versus Bi content with and without spin-orbit coupling for GaAs{sub 1-x}Bi{sub x} (at x=0.25, 0.50 and 0.75). Calculations are done with GGA. Highlights: Black-Right-Pointing-Pointer Structural and electronic properties of GaAs{sub 1-x}Bi{sub x} alloys were studied. Black-Right-Pointing-Pointer We present results of lattice constant, energy gap, bulk modulus and derivative. Black-Right-Pointing-Pointer The band gap decreases substantially with increasing Bi concentration. Black-Right-Pointing-Pointer Calculations of the density of states and charge densities are also presented. Black-Right-Pointing-Pointer We have performed calculations without and with spin-orbit coupling.

  10. Gallium Arsenide

    NASA Astrophysics Data System (ADS)

    Brozel, Mike

    The history of gallium arsenide is complicated because the technology required to produce GaAs devices has been fraught with problems associated with the material itself and with difficulties in its fabrication. Thus, for many years, GaAs was labelled as "the semiconductor of the future, and it will always be that way." Recently, however, advances in compact-disc (CD) technology, fibre-optic communications and mobile telephony have boosted investment in GaAs research and development. Consequently, there have been advances in materials and fabrication technology and, as a result, GaAs devices now enjoy stable niche markets.

  11. Gallium fluoroarsenates.

    PubMed

    Marshall, Kayleigh L; Armstrong, Jennifer A; Weller, Mark T

    2015-07-28

    Six new phases in the gallium-fluoride-arsenate system have been synthesised hydrofluorothermally using a fluoride-rich medium and "HAsF6" (HF : AsF5) as a reactant. RbGaF3(H2AsO4), KGaF(H2AsO4) and [piperazine-H2]2[Ga2F8(HAsO4)]·H2O have one dimensional structures, [DABCO-H2]2[Ga4F7O2H(AsO4)2]·4H2O consists of two dimensionally connected polyhedral layers, while GaF(AsO3[OH,F])2 and (NH4)3Ga4F9(AsO4)2 both have three-dimensionally connected polyhedral frameworks. PMID:26095086

  12. Compatibility of ITER candidate structural materials with static gallium

    SciTech Connect

    Luebbers, P.R.; Michaud, W.F.; Chopra, O.K.

    1993-12-01

    Tests were conducted on the compatibility of gallium with candidate structural materials for the International Thermonuclear Experimental Reactor, e.g., Type 316 SS, Inconel 625, and Nb-5 Mo-1 Zr alloy, as well as Armco iron, Nickel 270, and pure chromium. Type 316 stainless steel is least resistant to corrosion in static gallium and Nb-5 Mo-1 Zr alloy is most resistant. At 400{degrees}C, corrosion rates are {approx}4.0, 0.5, and 0.03 mm/yr for type 316 SS, Inconel 625, and Nb-5 Mo- 1 Zr alloy, respectively. The pure metals react rapidly with gallium. In contrast to findings in earlier studies, pure iron shows greater corrosion than nickel. The corrosion rates at 400{degrees}C are {ge}88 and 18 mm/yr, respectively, for Armco iron and Nickel 270. The results indicate that at temperatures up to 400{degrees}C, corrosion occurs primarily by dissolution and is accompanied by formation of metal/gallium intermetallic compounds. The solubility data for pure metals and oxygen in gallium are reviewed. The physical, chemical, and radioactive properties of gallium are also presented. The supply and availability of gallium, as well as price predictions through the year 2020, are summarized.

  13. Gallium nitride optoelectronic devices

    NASA Technical Reports Server (NTRS)

    Chu, T. L.; Chu, S. S.

    1972-01-01

    The growth of bulk gallium nitride crystals was achieved by the ammonolysis of gallium monochloride. Gallium nitride single crystals up to 2.5 x 0.5 cm in size were produced. The crystals are suitable as substrates for the epitaxial growth of gallium nitride. The epitaxial growth of gallium nitride on sapphire substrates with main faces of (0001) and (1T02) orientations was achieved by the ammonolysis of gallium monochloride in a gas flow system. The grown layers had electron concentrations in the range of 1 to 3 x 10 to the 19th power/cu cm and Hall mobilities in the range of 50 to 100 sq cm/v/sec at room temperature.

  14. Investigations in gallium removal

    SciTech Connect

    Philip, C.V.; Pitt, W.W.; Beard, C.A.

    1997-11-01

    Gallium present in weapons plutonium must be removed before it can be used for the production of mixed-oxide (MOX) nuclear reactor fuel. The main goal of the preliminary studies conducted at Texas A and M University was to assist in the development of a thermal process to remove gallium from a gallium oxide/plutonium oxide matrix. This effort is being conducted in close consultation with the Los Alamos National Laboratory (LANL) personnel involved in the development of this process for the US Department of Energy (DOE). Simple experiments were performed on gallium oxide, and cerium-oxide/gallium-oxide mixtures, heated to temperatures ranging from 700--900 C in a reducing environment, and a method for collecting the gallium vapors under these conditions was demonstrated.

  15. Isoelectronic Traps in Gallium Phosphide

    NASA Astrophysics Data System (ADS)

    Christian, Theresa; Alberi, Kirstin; Beaton, Daniel; Fluegel, Brian; Mascarenhas, Angelo

    2015-03-01

    Isoelectronic substitutional dopants can result in strongly localized exciton traps within a host bandstructure such as gallium arsenide (GaAs) or gallium phosphide (GaP). These traps have received great attention for their role in the anomalous bandgap bowing of nitrogen or bismuth-doped GaAs, creating the dramatic bandgap tunability of these unusual dilute alloys. In the wider, indirect-bandgap host material GaP, these same isoelectronic dopants create bound states within the gap that can have very high radiative efficiency and a wealth of discrete spectral transitions illuminating the symmetry of the localized excitonic trap state. We will present a comparative study of nitrogen and bismuth isoelectronic traps in GaP. Research was supported by the U. S. Department of Energy, Basic Energy Sciences, Materials Sciences and Engineering Division under contract DE-AC36-08GO28308 and by the Department of Energy Office of Science Graduate Fellowship Program (DOE SCGF), made possible in part by the American Recovery and Reinvestment Act of 2009, administered by ORISE-ORAU under contract no. DE-AC05-06OR23100.

  16. Preventing Supercooling Of Gallium

    NASA Technical Reports Server (NTRS)

    Massucco, Arthur A.; Wenghoefer, Hans M.; Wilkins, Ronnie

    1994-01-01

    Principle of heterogeneous nucleation exploited to prevent gallium from supercooling, enabling its use as heat-storage material that crystallizes reproducibly at its freezing or melting temperature of 29 to 30 degrees C. In original intended application, gallium used as heat-storage material in gloves of space suits. Terrestrial application lies in preparation of freezing-temperature reference samples for laboratories. Principle of heterogeneous nucleation also exploited similarly in heat pipes filled with sodium.

  17. Cu-Ga-Mn (Copper-Gallium-Manganese)

    NASA Astrophysics Data System (ADS)

    Materials Science International Team MSIT

    This document is part of Subvolume C2 'Non-Ferrous Metal Systems. Part 2: Selected Copper Systems' of Volume 11 'Ternary Alloy Systems - Phase Diagrams, Crystallographic and Thermodynamic Data critically evaluated by MSIT®' of Landolt-Börnstein - Group IV 'Physical Chemistry'. It provides data of the ternary system Copper-Gallium-Manganese.

  18. Visible light electroluminescent diodes of indium-gallium phosphide

    NASA Technical Reports Server (NTRS)

    Clough, R.; Richman, D.; Tietjen, J.

    1970-01-01

    Vapor deposition and acceptor impurity diffusion techniques are used to prepare indium-gallium phosphide junctions. Certain problems in preparation are overcome by altering gas flow conditions and by increasing the concentration of phosphine in the gas. A general formula is given for the alloy's composition.

  19. Gallium extraction by microemulsions.

    PubMed

    de Castro Dantas, T N; de Lucena Neto, M H; Dantas Neto, A A

    2002-04-01

    In this work, the use of microemulsion in the extraction of gallium, with Bayer process, has been studied. The studied microemulsion systems were: systems I and II, with saponified coconut oil (SCO) and 4-ethyl,1-methyl,7-octyl,8-hydroxyquinoleine (Kelex-100) as extractants. The extraction essays by microemulsion were carried out by applying an experimental planning method whose microemulsion points were prepared within an experimental domain favorable to the extraction. Gallium and aluminum extraction percentages, in each point, were evaluated via a statistical treatment of the data, with the use of variance analysis and mathematical models. In system I (SCO), percentages of extraction of 85.5% for gallium and 35.4% for aluminum were achieved; in system II (Kelex-100), the yields were 100% for gallium and 99.9% for aluminum. The reextraction study with sulfuric acid presented the same behavior for both systems, with efficiency depending upon the concentration of the acid, and allowing for a selective reextraction of gallium and aluminum. PMID:18968589

  20. Aluminum battery alloys

    DOEpatents

    Thompson, D.S.; Scott, D.H.

    1984-09-28

    Aluminum alloys suitable for use as anode structures in electrochemical cells are disclosed. These alloys include iron levels higher than previously felt possible, due to the presence of controlled amounts of manganese, with possible additions of magnesium and controlled amounts of gallium.

  1. Aluminum battery alloys

    DOEpatents

    Thompson, David S.; Scott, Darwin H.

    1985-01-01

    Aluminum alloys suitable for use as anode structures in electrochemical cs are disclosed. These alloys include iron levels higher than previously felt possible, due to the presence of controlled amounts of manganese, with possible additions of magnesium and controlled amounts of gallium.

  2. Gallium interactions with Zircaloy

    SciTech Connect

    Woods, A.L.; West, M.K.

    1999-01-01

    This study focuses on the effects of gallium ion implantation into zircaloy cladding material to investigate the effects that gallium may have in a reactor. High fluence ion implantation of Ga ions was conducted on heated Zircaloy-4 in the range of 10{sup 16}--10{sup 18} Ga ions/cm2. Surface effects were studied using SEM and electron microprobe analysis. The depth profile of Ga in the Zircaloy was characterized with Rutherford backscattering and SIMS techniques. Results indicate that the Zirc-4 is little affected up to a fluence of 10{sup 17} Ga ions/cm{sup 2}. After implantation of 10{sup 18} Ga ions/cm{sup 2}, sub-grain features on the order of 2 {micro}m were observed which may be due to intermetallic compound formation between Ga and Zr. For the highest fluence implant, Ga content in the Zirc-4 reached a saturation value of between 30 and 40 atomic %; significant enhanced diffusion was observed but gallium was not seen to concentrate at grain boundaries.

  3. Oxidative dissolution of gallium arsenide and separation of gallium from arsenic

    SciTech Connect

    Coleman, J.P.; Monzyk, B.F.

    1988-07-26

    The method of dissociating gallium arsenide into a gallium-containing component and an arsenic-containing component, is described which comprises contacting the gallium arsenide with an oxidizing agent and a liquid comprising hydroxamic acid to convert the gallium to a gallium-hydroxamic acid complex and to oxidize the arsenic to a positive valence state.

  4. Alloy

    NASA Astrophysics Data System (ADS)

    Cabeza, Sandra; Garcés, Gerardo; Pérez, Pablo; Adeva, Paloma

    2014-07-01

    The Mg98.5Gd1Zn0.5 alloy produced by a powder metallurgy route was studied and compared with the same alloy produced by extrusion of ingots. Atomized powders were cold compacted and extruded at 623 K and 673 K (350 °C and 400 °C). The microstructure of extruded materials was characterized by α-Mg grains, and Mg3Gd and 14H-LPSO particles located at grain boundaries. Grain size decreased from 6.8 μm in the extruded ingot, down to 1.6 μm for powders extruded at 623 K (350 °C). Grain refinement resulted in an increase in mechanical properties at room and high temperatures. Moreover, at high temperatures the PM alloy showed superplasticity at high strain rates, with elongations to failure up to 700 pct.

  5. Gallium nitride nanotube lasers

    DOE PAGESBeta

    Li, Changyi; Liu, Sheng; Hurtado, Antonio; Wright, Jeremy Benjamin; Xu, Huiwen; Luk, Ting Shan; Figiel, Jeffrey J.; Brener, Igal; Brueck, Steven R. J.; Wang, George T.

    2015-01-01

    Lasing is demonstrated from gallium nitride nanotubes fabricated using a two-step top-down technique. By optically pumping, we observed characteristics of lasing: a clear threshold, a narrow spectral, and guided emission from the nanotubes. In addition, annular lasing emission from the GaN nanotube is also observed, indicating that cross-sectional shape control can be employed to manipulate the properties of nanolasers. The nanotube lasers could be of interest for optical nanofluidic applications or application benefitting from a hollow beam shape.

  6. Gallium Arsenide Domino Circuit

    NASA Technical Reports Server (NTRS)

    Yang, Long; Long, Stephen I.

    1990-01-01

    Advantages include reduced power and high speed. Experimental gallium arsenide field-effect-transistor (FET) domino circuit replicated in large numbers for use in dynamic-logic systems. Name of circuit denotes mode of operation, which logic signals propagate from each stage to next when successive stages operated at slightly staggered clock cycles, in manner reminiscent of dominoes falling in a row. Building block of domino circuit includes input, inverter, and level-shifting substages. Combinational logic executed in input substage. During low half of clock cycle, result of logic operation transmitted to following stage.

  7. Gallium phosphide energy converters

    NASA Technical Reports Server (NTRS)

    Sims, P. E.; DiNetta, Louis C.; DuganCavanagh, K.; Goetz, M. A.

    1996-01-01

    Betavoltaic power supplies based on gallium phosphide can supply long term low-level power with high reliability. Results are presented for GaP devices powered by Ni-63 and tritiarated phosphors. Leakage currents as low as 1.2 x 10(exp -17) A/cm(exp 2) have been measured and the temperature dependence of the reverse saturation current is found to have ideal behavior. A small demonstration system has been assembled that generates and stores enough electricity to light up an LED.

  8. Fabrication of Aluminum Gallium Nitride/Gallium Nitride MESFET And It's Applications in Biosensing

    NASA Astrophysics Data System (ADS)

    Alur, Siddharth

    Gallium Nitride has been researched extensively for the past three decades for its application in Light Emitting Diodes (LED's), power devices and UV photodetectors. With the recent developments in crystal growth technology and the ability to control the doping there has been an increased interest in heterostructures formed between Gallium nitride and it's alloy Aluminium Gallium Nitride. These heterostructures due to the combined effect of spontaneous and piezoelectric effect can form a high density and a high mobility electron gas channel without any intentional doping. This high density electron gas makes these heterostructures ideal to be used as sensors. Gallium Nitride is also chemically very stable. Detection of biomolecules in a fast and reliable manner is very important in the areas of food safety and medical research. For biomolecular detection it is paramount to have a robust binding of the probes on the sensor surface. Therefore, in this dissertation, the fabrication and application of the AlGaN/GaN heterostructures as biological sensors for the detection of DNA and Organophosphate hydrolase enzyme is discussed. In order to use these AlGaN/GaN heterostructures as biological sensors capable of working in a liquid environment photodefinable polydimethyl-siloxane is used as an encapsulant. The immobilization conditions for a robust binding of thiolated DNA and the catalytic receptor enzyme organophosphate hydrolase on gold surfaces is developed with the help of X-ray photoelectron spectroscopy. DNA and OPH are detected by measuring the change in the drain current of the device as a function of time.

  9. Sputtering of tin and gallium-tin clusters

    SciTech Connect

    Lill, T.; Calaway, W.F.; Ma, Z.; Pellin, M.J.

    1994-08-01

    Tin and gallium-tin clusters have been produced by 4 keV Ar{sup +} ion bombardment of polycrystalline tin and the gallium-tin eutectic alloy and analyzed by time-of-flight mass spectrometry. The sputtered neutral species were photoionized with 193 nm (6.4 eV) excimer laser light. Neutral tin clusters containing up to 10 atoms and mixed gallium-tin clusters Ga{sub (n-m)}Sn{sub m} with n {<=} 4 for the neutrals and N {<=} 3 for the sputtered ionic species have been detected. Laser power density dependent intensity measurements, relative yields, and kinetic energy distributions have been measured. The abundance distributions of the mixed clusters have been found to be nonstatistical due to significant differences in the ionization efficiencies for clusters with equal nuclearity but different number of tin atoms. The results indicate that Ga{sub 2}Sn and Ga{sub 3}Sn like the all-gallium clusters have ionization potentials below 6.4 eV. In the case of Sn{sub 5}, Sn{sub 6}, GaSn and Ga{sub (n-m)}Sn{sub m} clusters with n=2 to 4 and m>1, the authors detect species that have sufficient internal energy to be one photon ionized despite ionization potentials that are higher 6.4 eV. The tin atom signal that is detected can be attributed to photofragmentation of dimers for both sputtering from polycrystalline tin and from the gallium-tin eutectic alloy.

  10. Electrospun Gallium Nitride Nanofibers

    SciTech Connect

    Melendez, Anamaris; Morales, Kristle; Ramos, Idalia; Campo, Eva; Santiago, Jorge J.

    2009-04-19

    The high thermal conductivity and wide bandgap of gallium nitride (GaN) are desirable characteristics in optoelectronics and sensing applications. In comparison to thin films and powders, in the nanofiber morphology the sensitivity of GaN is expected to increase as the exposed area (proportional to the length) increases. In this work we present electrospinning as a novel technique in the fabrication of GaN nanofibers. Electrospinning, invented in the 1930s, is a simple, inexpensive, and rapid technique to produce microscopically long ultrafine fibers. GaN nanofibers are produced using gallium nitrate and dimethyl-acetamide as precursors. After electrospinning, thermal decomposition under an inert atmosphere is used to pyrolyze the polymer. To complete the preparation, the nanofibers are sintered in a tube furnace under a NH{sub 3} flow. Both scanning electron microscopy and profilometry show that the process produces continuous and uniform fibers with diameters ranging from 20 to a few hundred nanometers, and lengths of up to a few centimeters. X-ray diffraction (XRD) analysis shows the development of GaN nanofibers with hexagonal wurtzite structure. Future work includes additional characterization using transmission electron microscopy and XRD to understand the role of precursors and nitridation in nanofiber synthesis, and the use of single nanofibers for the construction of optical and gas sensing devices.

  11. The interaction of gold with gallium arsenide

    NASA Technical Reports Server (NTRS)

    Weizer, Victor G.; Fatemi, Navid S.

    1988-01-01

    Gold and gold-based alloys, commonly used as solar-cell contact materials, are known to react readily with gallium arsenide. Experiments designed to identify the mechanisms involved in these GaAs-metal interactions have yielded several interesting results. It is shown that the reaction of GaAs with gold takes place via a dissociative diffusion process. It is shown further that the GaAs-metal reaction rate is controlled to a very great extent by the condition of the free surface of the contact metal, an interesting example of which is the previously unexplained increase in the reaction rate that has been observed for samples annealed in a vacuum environment as compared to those annealed in a gaseous ambient. A number of other hard-to-explain observations, such as the low-temperature formation of voids in the gold lattice and crystallite growth on the gold surface, are also explained by invoking this mechanism.

  12. Contact formation in gallium arsenide solar cells

    NASA Technical Reports Server (NTRS)

    Weizer, Victor G.; Fatemi, Navid S.

    1988-01-01

    Gold and gold-based alloys, commonly used as solar cell contact materials, are known to react readily with gallium arsenide. Experiments were performed to identify the mechanisms involved in these GaAs-metal interactions. It is shown that the reaction of GaAs with gold takes place via a dissociative diffusion process. It is shown further that the GaAs-metal reaction rate is controlled to a very great extent by the condition of the free surface of the contact metal, an interesting example of which is the previously unexplained increase in the reaction rate that has been observed for samples annealed in a vacuum environment as compared to those annealed in a gaseous ambient. A number of other hard-to-explain observations, such as the low-temperature formation of voids in the gold lattice and crystallite growth on the gold surface, are explained by invoking this mechanism.

  13. Gallium-positive tumor thrombus

    SciTech Connect

    Wenzel, D.J.

    1984-01-01

    A case is presented in which both a clear cell renal tumor and its accurate intravenous propagation were preoperatively depicted by combined information from tomographic gallium imaging and CT scanning.

  14. Gallium localization in dissecting aortic aneurysm

    SciTech Connect

    Haden, H.T.; Lippman, H.R.

    1988-08-01

    Gallium concentration was demonstrated in a dissecting aneurysm of the aortic arch, imaged approximately 2 weeks after dissection. Concentration of gallium was apparently due to the inflammatory reaction associated with the organizing intramural hematoma.

  15. Gallium phosphide energy converters

    NASA Technical Reports Server (NTRS)

    Sims, P. E.; Dinetta, L. C.; Goetz, M. A.

    1995-01-01

    Gallium phosphide (GaP) energy converters may be successfully deployed to provide new mission capabilities for spacecraft. Betavoltaic power supplies based on the conversion of tritium beta decay to electricity using GaP energy converters can supply long term low-level power with high reliability. High temperature solar cells, also based on GaP, can be used in inward-bound missions greatly reducing the need for thermal dissipation. Results are presented for GaP direct conversion devices powered by Ni-63 and compared to the conversion of light emitted by tritiarated phosphors. Leakage currents as low as 1.2 x 10(exp -17) A/sq cm have been measured and the temperature dependence of the reverse saturation current is found to have ideal behavior. Temperature dependent IV, QE, R(sub sh), and V(sub oc) results are also presented. These data are used to predict the high-temperature solar cell and betacell performance of GaP devices and suggest appropriate applications for the deployment of this technology.

  16. Effect of oxidation on the mechanical properties of liquid gallium and eutectic gallium-indium

    NASA Astrophysics Data System (ADS)

    Xu, Qin; Oudalov, Nikolai; Guo, Qiti; Jaeger, Heinrich M.; Brown, Eric

    2012-06-01

    Liquid metals exhibit remarkable mechanical properties, in particular large surface tension and low viscosity. However, these properties are greatly affected by oxidation when exposed to air. We measure the viscosity, surface tension, and contact angle of gallium and a eutectic gallium-indium alloy while controlling such oxidation by surrounding the metals with an acid bath of variable concentration. Rheometry measurements reveal a yield stress directly attributable to an oxide skin that obscures the intrinsic behavior of the liquid metals. We demonstrate how the intrinsic viscosity can be obtained with precision through a scaling technique that collapses low- and high-Reynolds number data. Measuring surface tension with a pendant drop method, we show that the oxide skin generates a surface stress that mimics surface tension and develop a simple model to relate this to the yield stress obtained from rheometry. We find that yield stress, surface tension, and contact angle all transition from solid-like to liquid behavior at the same critical acid concentration, thereby quantitatively confirming that the wettability of these liquid metals is due to the oxide skin.

  17. Medical Applications and Toxicities of Gallium Compounds

    PubMed Central

    Chitambar, Christopher R.

    2010-01-01

    Over the past two to three decades, gallium compounds have gained importance in the fields of medicine and electronics. In clinical medicine, radioactive gallium and stable gallium nitrate are used as diagnostic and therapeutic agents in cancer and disorders of calcium and bone metabolism. In addition, gallium compounds have displayed anti-inflammatory and immunosuppressive activity in animal models of human disease while more recent studies have shown that gallium compounds may function as antimicrobial agents against certain pathogens. In a totally different realm, the chemical properties of gallium arsenide have led to its use in the semiconductor industry. Gallium compounds, whether used medically or in the electronics field, have toxicities. Patients receiving gallium nitrate for the treatment of various diseases may benefit from such therapy, but knowledge of the therapeutic index of this drug is necessary to avoid clinical toxicities. Animals exposed to gallium arsenide display toxicities in certain organ systems suggesting that environmental risks may exist for individuals exposed to this compound in the workplace. Although the arsenic moiety of gallium arsenide appears to be mainly responsible for its pulmonary toxicity, gallium may contribute to some of the detrimental effects in other organs. The use of older and newer gallium compounds in clinical medicine may be advanced by a better understanding of their mechanisms of action, drug resistance, pharmacology, and side-effects. This review will discuss the medical applications of gallium and its mechanisms of action, the newer gallium compounds and future directions for development, and the toxicities of gallium compounds in current use. PMID:20623028

  18. Synthesis and characterization of salt scrub alloys

    SciTech Connect

    Pritchett, S.R.; Moore, J.J.; Mishra, B.; Olson, D.L.

    1992-07-25

    Lithium and calcium gallides have been synthesized in stoichiometries that can be used as reduction alloys for the Rocky Flats Plant salt-scrub process. The salt scrub process is performed to recover valuable metals from salts generated in the electrorefining and the molten salt extraction processes. Combustion synthesis in the thermal explosion mode has been accomplished successfully with suitable reactants to provide a significant amount of exothermic heat in the lithium-gallium and lithium-aluminum systems. The combustion synthesis reactions were optimized with respect to green theoretical density, powder particle size, and heating rate. The required salt scrub compositions were achieved by adding additional reductant to the combustion synthesized intermetallic compound. Combustion synthesis in the calcium-gallium system was not successful, apparently owing to the large calcium particle size (>850 {mu}m), although a significant level of exothermicity was observed. Therefore, the calcium-gallium salt-scrub alloys were produced by pressing and sintering into pellet form. The microstructural evolution during sintering, oxidation behavior, and cerium choride scrubbing ability were examined for the calcium-gallium pellets. Lithium-gallium salt-scrub alloys could not be produced by pressing owing to the fine lithium particle size employed (<45 {mu}m). It is hypothesized that the lithium-gallium salt scrub alloys can be pressed by utilizing coarser lithium ({approx_equal} 1 mm). 60 refs., 58 figs., 5 tabs.

  19. Mineral resource of the month: gallium

    USGS Publications Warehouse

    Jaskula, Brian

    2009-01-01

    The metal element gallium occurs in very small concentrations in rocks and ores of other metals — native gallium is not known. As society gets more and more high-tech, gallium becomes more useful. Gallium is one of only five metals that are liquid at or close to room temperature. It has one of the longest liquid ranges of any metal (29.8 degrees Celsius to 2204 degrees Celsius) and has a low vapor pressure even at high temperatures. Ultra-pure gallium has a brilliant silvery appearance, and the solid metal exhibits conchoidal fracture similar to glass.

  20. Gallium nanoparticle plasmonics

    NASA Astrophysics Data System (ADS)

    Yang, Yang; Wu, Pae C.; Kim, Tong-Ho; Brown, April S.; Everitt, Henry O.

    2010-03-01

    Gallium nanoparticles(Ga NPs) exhibit surface plasmon resonance(SPR) wavelengths that can extend deep into the UV. Because Ga NPs also possess high thermal stability and long lifetimes(months), they may be exploited for UV surface enhanced Raman spectroscopy. Raman enhancement arises from the local field factor g(w) which can be calculated using the Clausius-Mosotti relation for free standing NPs much smaller than the laser wavelength. In this case, |g(w)|2 for Ga NPs is >50 at a wavelength <190nm, compared to 26 for Au at 526nm and 240 for Ag at 345nm. This enhancement occurs over a much wider bandwidth in Ga(>10000 cm-1) than in Au(2100 cm-1) or Ag(6100 cm-1). To explore the potential of Ga plasmonics, molecular beam epitaxy was used to synthesize Ga NPs on solid supports. For deposition on sapphire, elevating the deposition temperature from 300K to 1000K increases Ga desorption and dramatically narrows the NP size distribution without changing the SPR wavelength. To study the role of substrate polarity, Ga NPs were also deposited at 300K on Si-polar and C-polar SiC. The mean size of NPs, which scales inversely with the surface diffusion barrier energy, is 1.8 times larger for Si-polar than for C-polar substrates. This result is consistent with the observed barrier energies 0.72eV for Si-Ga and 1.81eV for C-Ga.

  1. Potential effects of gallium on cladding materials

    SciTech Connect

    Wilson, D.F.; Beahm, E.C.; Besmann, T.M.; DeVan, J.H.; DiStefano, J.R.; Gat, U.; Greene, S.R.; Rittenhouse, P.L.; Worley, B.A.

    1997-10-01

    This paper identifies and examines issues concerning the incorporation of gallium in weapons derived plutonium in light water reactor (LWR) MOX fuels. Particular attention is given to the more likely effects of the gallium on the behavior of the cladding material. The chemistry of weapons grade (WG) MOX, including possible consequences of gallium within plutonium agglomerates, was assessed. Based on the calculated oxidation potentials of MOX fuel, the effect that gallium may have on reactions involving fission products and possible impact on cladding performance were postulated. Gallium transport mechanisms are discussed. With an understanding of oxidation potentials and assumptions of mechanisms for gallium transport, possible effects of gallium on corrosion of cladding were evaluated. Potential and unresolved issues and suggested research and development (R and D) required to provide missing information are presented.

  2. Renal amyloidosis. Evaluation by gallium imaging

    SciTech Connect

    Lee, V.W.; Skinner, M.; Cohen, A.S.; Ngai, S.; Peng, T.T.

    1986-09-01

    A study has been performed to evaluate the efficacy of gallium imaging in the detection of renal amyloidosis. Ten of the 11 patients who had biopsy-proven renal amyloidosis demonstrated marked uptake in both kidneys. One patient revealed moderate gallium uptake in his kidneys. None of the patients had underlying renal or extrarenal pathology other than amyloidosis, which could account for renal gallium uptake (renal infection, neoplasm, hepatic failure or frequent blood transfusions). Four patients also had extrarenal foci of abnormal gallium uptake, suggesting other sites of amyloid deposits. Our data strongly suggest that gallium imaging has a high sensitivity for detection of renal amyloidosis. Its specificity is enhanced significantly by careful review of the clinical history to exclude other known causes of renal gallium uptake. Potentially, gallium imaging may be used to monitor the progress of patients under experimental therapy.

  3. Examples of liquiq metal embrittlement in industrial aluminium alloys

    NASA Astrophysics Data System (ADS)

    Bréchet, Y.; Rodine, A.; Véron, M.; Péron, S.; Deschamps, A.

    2002-09-01

    Liquid metal embrittlement (LME) phenomena were investigated in two industrial aluminium alloys. Gallium penetration in 7010 alloys was systematically investigated to shed light on the effect of microstructure and plasticity ahead of the crack tip. Hot temperature shortness in 5083 alloy is given as an example of cleavage induced by LME.

  4. Liquid gallium rotary electric contract

    NASA Technical Reports Server (NTRS)

    Przybyszewski, J. S.

    1969-01-01

    Due to its low vapor pressure, gallium, when substituted for mercury in a liquid slip ring system, transmits substantial amounts of electrical current to rotating components in an ultrahigh vacuum. It features low electrical loss, little or no wear, and long maintenance-free life.

  5. Gallium scan in intracerebral sarcoidosis

    SciTech Connect

    Makhija, M.C.; Anayiotos, C.P.

    1981-07-01

    Sarcoidosis involving the nervous system probably occurs in about 4% of patients. The usefulness of brain scintigraphy in these cases has been suggested. In this case of cerebral sarcoid granuloma, gallium imaging demonstrated the lesion before treatment and showed disappearance of the lesion after corticosteroid treatment, which correlated with the patient's clinical improvement.

  6. P-type gallium nitride

    DOEpatents

    Rubin, M.; Newman, N.; Fu, T.; Ross, J.; Chan, J.

    1997-08-12

    Several methods have been found to make p-type gallium nitride. P-type gallium nitride has long been sought for electronic devices. N-type gallium nitride is readily available. Discovery of p-type gallium nitride and the methods for making it will enable its use in ultraviolet and blue light-emitting diodes and lasers. pGaN will further enable blue photocathode elements to be made. Molecular beam epitaxy on substrates held at the proper temperatures, assisted by a nitrogen beam of the proper energy produced several types of p-type GaN with hole concentrations of about 5{times}10{sup 11} /cm{sup 3} and hole mobilities of about 500 cm{sup 2} /V-sec, measured at 250 K. P-type GaN can be formed of unintentionally-doped material or can be doped with magnesium by diffusion, ion implantation, or co-evaporation. When applicable, the nitrogen can be substituted with other group III elements such as Al. 9 figs.

  7. P-type gallium nitride

    DOEpatents

    Rubin, Michael; Newman, Nathan; Fu, Tracy; Ross, Jennifer; Chan, James

    1997-01-01

    Several methods have been found to make p-type gallium nitride. P-type gallium nitride has long been sought for electronic devices. N-type gallium nitride is readily available. Discovery of p-type gallium nitride and the methods for making it will enable its use in ultraviolet and blue light-emitting diodes and lasers. pGaN will further enable blue photocathode elements to be made. Molecular beam epitaxy on substrates held at the proper temperatures, assisted by a nitrogen beam of the proper energy produced several types of p-type GaN with hole concentrations of about 5.times.10.sup.11 /cm.sup.3 and hole mobilities of about 500 cm.sup.2 /V-sec, measured at 250.degree. K. P-type GaN can be formed of unintentionally-doped material or can be doped with magnesium by diffusion, ion implantation, or co-evaporation. When applicable, the nitrogen can be substituted with other group III elements such as Al.

  8. Gallium nitride electronics

    NASA Astrophysics Data System (ADS)

    Rajan, Siddharth; Jena, Debdeep

    2013-07-01

    In the past two decades, there has been increasing research and industrial activity in the area of gallium nitride (GaN) electronics, stimulated first by the successful demonstration of GaN LEDs. While the promise of wide band gap semiconductors for power electronics was recognized many years before this by one of the contributors to this issue (J Baliga), the success in the area of LEDs acted as a catalyst. It set the field of GaN electronics in motion, and today the technology is improving the performance of several applications including RF cell phone base stations and military radar. GaN could also play a very important role in reducing worldwide energy consumption by enabling high efficiency compact power converters operating at high voltages and lower frequencies. While GaN electronics is a rapidly evolving area with active research worldwide, this special issue provides an opportunity to capture some of the great advances that have been made in the last 15 years. The issue begins with a section on epitaxy and processing, followed by an overview of high-frequency HEMTs, which have been the most commercially successful application of III-nitride electronics to date. This is followed by review and research articles on power-switching transistors, which are currently of great interest to the III-nitride community. A section of this issue is devoted to the reliability of III-nitride devices, an area that is of increasing significance as the research focus has moved from not just high performance but also production-worthiness and long-term usage of these devices. Finally, a group of papers on new and relatively less studied ideas for III-nitride electronics, such as interband tunneling, heterojunction bipolar transistors, and high-temperature electronics is included. These areas point to new areas of research and technological innovation going beyond the state of the art into the future. We hope that the breadth and quality of articles in this issue will make it an excellent reference for newcomers and experienced researchers in this field for several years. We thank Alice Malhador at IOP Publishing for her constant encouragement and guidance in putting together this special issue on GaN electronics.

  9. A study of the applicability of gallium arsenide and silicon carbide as aerospace sensor materials

    NASA Technical Reports Server (NTRS)

    Hurley, John S.

    1990-01-01

    Most of the piezoresistive sensors, to date, are made of silicon and germanium. Unfortunately, such materials are severly restricted in high temperature environments. By comparing the effects of temperature on the impurity concentrations and piezoresistive coefficients of silicon, gallium arsenide, and silicon carbide, it is being determined if gallium arsenide and silicon carbide are better suited materials for piezoresistive sensors in high temperature environments. The results show that the melting point for gallium arsenide prevents it from solely being used in high temperature situations, however, when used in the alloy Al(x)Ga(1-x)As, not only the advantage of the wider energy band gas is obtained, but also the higher desire melting temperature. Silicon carbide, with its wide energy band gap and higher melting temperature suggests promise as a high temperature piezoresistive sensor.

  10. Epitaxial Deposition Of Germanium Doped With Gallium

    NASA Technical Reports Server (NTRS)

    Huffman, James E.

    1994-01-01

    Epitaxial layers of germanium doped with gallium made by chemical vapor deposition. Method involves combination of techniques and materials used in chemical vapor deposition with GeH4 or GeCl4 as source of germanium and GaCl3 as source of gallium. Resulting epitaxial layers of germanium doped with gallium expected to be highly pure, with high crystalline quality. High-quality material useful in infrared sensors.

  11. Collector for recovering gallium from weapons plutonium

    SciTech Connect

    Philip, C.V.; Anthony, R.G.; Chokkaram, S.

    1998-09-01

    Currently, the separation of gallium from weapons plutonium involves the use of aqueous processing using either solvent extraction of ion exchange. However, this process generates significant quantities of liquid radioactive wastes. A Thermally Induced Gallium Removal process, or TIGR, developed by researchers at Los Alamos National Laboratories, is a simpler alternative to aqueous processing. This research examined this process, and the behavior of gallium suboxide, a vapor that is swept away by passing hydrogen/argon over gallium trioxide/plutonium oxide heated at 1100 C during the TIGR process. Through experimental procedures, efforts were made to prevent the deposition of corrosive gallium onto furnace and vent surfaces. Experimental procedures included three options for gallium removal and collection: (1) collection of gallium suboxide through use of a cold finger; (2) collection by in situ air oxidation; and (3) collection of gallium on copper. Results conclude all three collection mechanisms are feasible. In addition, gallium trioxide exists in three crystalline forms, and each form was encountered during each experiment, and that each form will have a different reactivity.

  12. Decreased gallium uptake in acute hematogenous osteomyelitis

    SciTech Connect

    Ang, J.G.; Gelfand, M.J.

    1983-07-01

    Decreased radiopharmaceutical uptake was noted on both bone and gallium scans in the case of acute hematogenous osteomyelitis of the right ilium (acetabular roof). This combination of findings is probably rare. The mechanism of decreased gallium uptake is unknown, but may be related to decreased blood flow.

  13. Gallium Electromagnetic (GEM) Thrustor Concept and Design

    NASA Technical Reports Server (NTRS)

    Polzin, Kurt A.; Markusic, Thomas E.

    2006-01-01

    We describe the design of a new type of two-stage pulsed electromagnetic accelerator, the gallium electromagnetic (GEM) thruster. A schematic illustration of the GEM thruster concept is given in Fig. 1. In this concept, liquid gallium propellant is pumped into the first stage through a porous metal electrode using an electromagneticpump[l]. At a designated time, a pulsed discharge (approx.10-50 J) is initiated in the first stage, ablating the liquid gallium from the porous electrode surface and ejecting a dense thermal gallium plasma into the second state. The presence of the gallium plasma in the second stage serves to trigger the high-energy (approx.500 I), send-stage puke which provides the primary electromagnetic (j x B) acceleration.

  14. Clinical Applications of Gallium-68

    PubMed Central

    Banerjee, Sangeeta Ray; Pomper, Martin G.

    2013-01-01

    Gallium-68 is a positron-emitting radioisotope that is produced from a 68Ge/68Ga generator. As such it is conveniently used, decoupling radiopharmacies from the need for a cyclotron on site. Gallium-68-labeled peptides have been recognized as a new class of radiopharmaceuticals showing fast target localization and blood clearance. 68Ga-DOTATOC, 8Ga-DOTATATE, 68Ga-DOTANOC, are the most prominent radiopharmaceuticals currently in use for imaging and differentiating lesions of various somatostatin receptor subtypes, overexpressed in many neuroendocrine tumors. There has been a tremendous increase in the number of clinical studies with 68Ga over the past few years around the world, including within the United States. An estimated ~10,000 scans are being performed yearly in Europe at about 100 centers utilizing 68Ga-labeled somatostatin analogs within clinical trials. Two academic sites within the US have also begun to undertake human studies. This review will focus on the clinical experience of selected, well-established and recently applied 68Ga-labeled imaging agents used in nuclear medicine. PMID:23522791

  15. Electrospun Gallium Nitride Nanofibers (abstract)

    NASA Astrophysics Data System (ADS)

    Meléndez, Anamaris; Morales, Kristle; Ramos, Idalia; Campo, Eva; Santiago, Jorge J.

    2009-04-01

    The high thermal conductivity and wide bandgap of gallium nitride (GaN) are desirable characteristics in optoelectronics and sensing applications. In comparison to thin films and powders, in the nanofiber morphology the sensitivity of GaN is expected to increase as the exposed area (proportional to the length) increases. In this work we present electrospinning as a novel technique in the fabrication of GaN nanofibers. Electrospinning, invented in the 1930s, is a simple, inexpensive, and rapid technique to produce microscopically long ultrafine fibers. GaN nanofibers are produced using gallium nitrate and dimethyl-acetamide as precursors. After electrospinning, thermal decomposition under an inert atmosphere is used to pyrolyze the polymer. To complete the preparation, the nanofibers are sintered in a tube furnace under a NH3 flow. Both scanning electron microscopy and profilometry show that the process produces continuous and uniform fibers with diameters ranging from 20 to a few hundred nanometers, and lengths of up to a few centimeters. X-ray diffraction (XRD) analysis shows the development of GaN nanofibers with hexagonal wurtzite structure. Future work includes additional characterization using transmission electron microscopy and XRD to understand the role of precursors and nitridation in nanofiber synthesis, and the use of single nanofibers for the construction of optical and gas sensing devices.

  16. Status of gallium-67 in tumor detector

    SciTech Connect

    Hoffer, P.

    1980-04-01

    The efficacy of gallium-67 citrate in detecting specific tumors is discussed. Tumors in which gallium-67 imaging is useful as a diagnostic tool include Hodgkin's disease, histiocystic lymphoma, Burkitt's lymphoma, hepatoma melanoma, and leukemia. It has not been found to be effective in diagnosing head and neck tumors, gastrointestinal tumors, genitourinary tract tumors, breast tumors, and pediatric tumors. Gallium may be useful in the evaluation of non-Hodgkin's lymphoma, testicular carcinoma, mesothelioma, and carcinoma of the lung. It may also be useful for determining response to treatment and prognosis in some neoplasms.

  17. The surface tension of liquid gallium

    NASA Technical Reports Server (NTRS)

    Hardy, S. C.

    1985-01-01

    The surface tension of liquid gallium has been measured using the sessile drop technique in an Auger spectrometer. The experimental method is described. The surface tension in mJ/sq m is found to decrease linearly with increasing temperature and may be represented as 708-0.66(T-29.8), where T is the temperature in centigrade. This result is of interest because gallium has been suggested as a model fluid for Marangoni flow experiments. In addition, the surface tension is of technological significance in the processing of compound semiconductors involving gallium.

  18. In vitro bio-functionality of gallium nitride sensors for radiation biophysics

    SciTech Connect

    Hofstetter, Markus; Howgate, John; Schmid, Martin; Schoell, Sebastian; Sachsenhauser, Matthias; Adiguezel, Denis; Stutzmann, Martin; Sharp, Ian D.; Thalhammer, Stefan

    2012-07-27

    Highlights: Black-Right-Pointing-Pointer Gallium nitride based sensors show promising characteristics to monitor cellular parameters. Black-Right-Pointing-Pointer Cell growth experiments reveal excellent biocompatibiltiy of the host GaN material. Black-Right-Pointing-Pointer We present a biofunctionality assay using ionizing radiation. Black-Right-Pointing-Pointer DNA repair is utilized to evaluate material induced alterations in the cellular behavior. Black-Right-Pointing-Pointer GaN shows no bio-functional influence on the cellular environment. -- Abstract: There is an increasing interest in the integration of hybrid bio-semiconductor systems for the non-invasive evaluation of physiological parameters. High quality gallium nitride and its alloys show promising characteristics to monitor cellular parameters. Nevertheless, such applications not only request appropriate sensing capabilities but also the biocompatibility and especially the biofunctionality of materials. Here we show extensive biocompatibility studies of gallium nitride and, for the first time, a biofunctionality assay using ionizing radiation. Analytical sensor devices are used in medical settings, as well as for cell- and tissue engineering. Within these fields, semiconductor devices have increasingly been applied for online biosensing on a cellular and tissue level. Integration of advanced materials such as gallium nitride into these systems has the potential to increase the range of applicability for a multitude of test devices and greatly enhance sensitivity and functionality. However, for such applications it is necessary to optimize cell-surface interactions and to verify the biocompatibility of the semiconductor. In this work, we present studies of mouse fibroblast cell activity grown on gallium nitride surfaces after applying external noxa. Cell-semiconductor hybrids were irradiated with X-rays at air kerma doses up to 250 mGy and the DNA repair dynamics, cell proliferation, and cell growth dynamics of adherent cells were compared to control samples. The impact of ionizing radiation on DNA, along with the associated cellular repair mechanisms, is well characterized and serves as a reference tool for evaluation of substrate effects. The results indicate that gallium nitride does not require specific surface treatments to ensure biocompatibility and suggest that cell signaling is not affected by micro-environmental alterations arising from gallium nitride-cell interactions. The observation that gallium nitride provides no bio-functional influence on the cellular environment confirms that this material is well suited for future biosensing applications without the need for additional chemical surface modification.

  19. Gallium-67 activity in bronchoalveolar lavage fluid in sarcoidosis

    SciTech Connect

    Trauth, H.A.; Heimes, K.; Schubotz, R.; von Wichert, P.

    1986-01-01

    Roentgenograms and gallium-67 scans and gallium-67 counts of BAL fluid samples, together with differential cell counts, have proved to be useful in assessing activity and lung involvement in sarcoidosis. In active pulmonary sarcoidosis gallium-67 scans are usually positive. Quantitation of gallium-67 uptake in lung scans, however, may be difficult. Because gallium-67 uptake and cell counts in BAL fluid may be correlated, we set out to investigate gallium-67 activity in BAL fluid recovered from patient of different groups. Sixteen patients with recently diagnosed and untreated sarcoidosis, nine patients with healthy lungs, and five patients with CFA were studied. Gallium-67 uptake of the lung, gallium-67 activity in the lavage fluid, SACE and LACE levels, and alpha 1-AT activity were measured. Significantly more gallium-67 activity was found in BAL fluid from sarcoidosis patients than in that from CFA patients (alpha = .001) or patients with healthy lungs (alpha = .001). Gallium-67 activity in BAL fluid could be well correlated with the number of lymphocytes in BAL fluid, but poorly with the number of macrophages. Subjects with increased levels of SACE or serum alpha 1-AT showed higher lavage gallium-67 activity than did normals, but no correlation could be established. High gallium-67 activity in lavage fluid may be correlated with acute sarcoidosis or physiological deterioration; low activity denotes change for the better. The results show that gallium-67 counts in BAL fluid reflects the intensity of gallium-67 uptake and thus of activity of pulmonary sarcoidosis.

  20. Radiochemical separation of gallium by amalgam exchange

    USGS Publications Warehouse

    Ruch, R.R.

    1969-01-01

    An amalgam-exchange separation of radioactive gallium from a number of interfering radioisotopes has been developed. A dilute (ca. 0.3%) gallium amalgam is agitated with a slightly acidic solution of 72Ga3+ containing concentrations of sodium thiocyanate and either perchlorate or chloride. The amalgam is then removed and the radioactive gallium stripped by agitation with dilute nitric acid. The combined exchange yield of the perchlorate-thiocyanate system is 90??4% and that of the chloride-thiocyanate system is 75??4%. Decontamination yields of most of the 11 interfering isotopes studied were less than 0.02%. The technique is applicable for use with activation analysis for the determination of trace amounts of gallium. ?? 1969.

  1. Development of gallium arsenide solar cells

    NASA Technical Reports Server (NTRS)

    1973-01-01

    The potential of ion implantation as a means of developing gallium arsenide solar cells with high efficiency performance was investigated. Computer calculations on gallium arsenide cell characteristics are presented to show the effects of surface recombination, junction space-charge recombination, and built-in fields produced by nonuniform doping of the surface region. The fabrication technology is summarized. Electrical and optical measurements on samples of solar cells are included.

  2. Generator for gallium-68 and compositions obtained therefrom

    DOEpatents

    Neirinckx, Rudi D.; Davis, Michael A.

    1981-01-01

    A generator for obtaining radioactive gallium-68 from germanium-68 bound in a resin containing unsubstituted phenolic hydroxyl groups. The germanium-68 is loaded into the resin from an aqueous solution of the germanium-68. A physiologically acceptable solution of gallium-68 having an activity of 0.1 to 50 millicuries per milliliter of gallium-68 solution is obtained. The solution is obtained from the bound germanium-68 which forms gallium-68 in situ by eluting the column with a hydrochloric acid solution to form an acidic solution of gallium-68. The acidic solution of gallium-68 can be neutralized.

  3. The solubility of hydrogen and deuterium in alloyed, unalloyed and impure plutonium metal

    SciTech Connect

    Richmond, Scott; Bridgewater, Jon S; Ward, John W; Allen, Thomas A

    2009-01-01

    Pressure-Composition-Temperature (PCT) data are presented for the plutonium-hydrogen (Pu-H) and plutonium-deuterium (Pu-D) systems in the solubility region up to terminal solubility (precipitation of PuH{sub 2}). The heats of solution for PuH{sub s} and PuD{sub s} are determined from PCT data in the ranges 350-625 C for gallium alloyed Pu and 400-575 C for unalloyed Pu. The solubility of high purity plutonium alloyed with 2 at.% gallium is compared to high purity unalloyed plutonium. Significant differences are found in hydrogen solubility for unalloyed Pu versus gallium alloyed Pu. Differences in hydrogen solubility due to an apparent phase change are observable in the alloyed and unalloyed solubilities. The effect of iron impurities on Pu-Ga alloyed Pu is shown via hydrogen solubility data as preventing complete homogenization.

  4. Gallium-67 scanning for malignant melanoma

    SciTech Connect

    Kagan, R.; Witt, T.; Bines, S.; Mesleh, G.; Economou, S.

    1988-01-15

    Melanoma is characterized by a tendency to metastasize widely throughout the body and its relative affinity for gallium-67. Because of the ability of this nuclide to image tumor sites in numerous organ systems, it has been used to detect metastases in patients with malignant melanoma. The effectiveness of this technique, however, has been controversial. This article documents the retrospective analysis of results from 296 gallium-67 scintiscans from 222 patients with melanoma. Patients were placed in two groups. The low suspicion group (148 patients undergoing 191 scans) consisted of patients with no evidence of disease; the gallium scans were performed solely for screening purposes. There were 175 true-negative scans, nine true-positive scans (eight of the nine were positive only at the untreated primary site), three false-negative scans, and four false-positive scans. Therefore, in only one patient (0.5%) did a screening gallium scan reveal disease that was not expected. The high suspicion group (85 patients undergoing 105 scans) consisted of patients with established evidence of metastatic disease; the gallium scan was performed to confirm those findings and to search for involvement of other organ systems. Of these scans, ten were true-negative, 73 true-positive, 21 false-negative, and one false-positive. In this group the 20% false-negative results indicate that gallium scanning is considerably less sensitive than the combination of clinical and standard radiographic assessment. It was concluded that gallium-67 scintiscanning of patients with melanoma, whether for screening or evaluation of patients with known metastases, provides little information that affects clinical staging or therapeutic design. Therefore, the technique is of limited value for routinely investigating the extent of disease.

  5. Speciation of scandium and gallium in soil.

    PubMed

    Połedniok, Justyna

    2008-09-01

    A method for the speciation of scandium and gallium in soil has been developed. The sequential extraction scheme of Tessier et al. for heavy metals was examined for the scandium and gallium separation. The regents proposed by Tessier were used for the extraction, and only for the residual fraction the HClO4 was replaced with H2SO4. The optimum conditions for leaching scandium and gallium from the soil were chosen for each fraction. Very sensitive, spectrophotometric methods based on the mixed complexes of Sc(III) and Ga(III) with Chrome Azurol S and benzyldodecyldimethylammonium bromide were applied for the scandium and gallium determination after their separation by solvent extraction. 100% mesityl oxide and a 0.5M solution of 2-thenoyltrifluoroacetone in xylene were chosen for the extraction of scandium and butyl acetate was selected for gallium. Soil samples from two different regions of Poland were the object of this research. The content of scandium and gallium found in the individual fractions of Upper Silesia soil (industrial region) was [in microgg(-1)] Sc: I, 1.52; II, 0.53; III, 7.78; IV, 1.79; V, 0.20; Ga: I, 24.7; III, 29.2; IV, 35.4; V, 6.9. In Podlasie soil (agricultural region), the content of both elements was clearly lower. The total content of scandium and gallium in the five soil fractions was in good correlation with the total content of these elements in the soils found after HF-H2SO4 digestion. Analysis using the ICP-OES method gave comparable results. PMID:18653213

  6. Window structure for passivating solar cells based on gallium arsenide

    NASA Technical Reports Server (NTRS)

    Barnett, Allen M. (Inventor)

    1985-01-01

    Passivated gallium arsenide solar photovoltaic cells with high resistance to moisture and oxygen are provided by means of a gallium arsenide phosphide window graded through its thickness from arsenic rich to phosphorus rich.

  7. Controlled Electrochemical Deformation of Liquid-Phase Gallium.

    PubMed

    Chrimes, Adam F; Berean, Kyle J; Mitchell, Arnan; Rosengarten, Gary; Kalantar-Zadeh, Kourosh

    2016-02-17

    Pure gallium is a soft metal with a low temperature melting point of 29.8 °C. This low melting temperature can potentially be employed for creating optical components with changeable configurations on demand by manipulating gallium in its liquid state. Gallium is a smooth and highly reflective metal that can be readily maneuvered using electric fields. These features allow gallium to be used as a reconfigurable optical reflector. This work demonstrates the use of gallium for creating reconfigurable optical reflectors manipulated through the use of electric fields when gallium is in a liquid state. The use of gallium allows the formed structures to be frozen and preserved as long as the temperature of the metal remains below its melting temperature. The lens can be readily reshaped by raising the temperature above the melting point and reapplying an electric field to produce a different curvature of the gallium reflector. PMID:26820807

  8. 40 CFR 721.10391 - Copper gallium indium selenide.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Copper gallium indium selenide. 721... Substances § 721.10391 Copper gallium indium selenide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as copper gallium indium selenide (PMN...

  9. 40 CFR 721.10391 - Copper gallium indium selenide.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Copper gallium indium selenide. 721... Substances § 721.10391 Copper gallium indium selenide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as copper gallium indium selenide (PMN...

  10. Gallium Zeolites for Light Paraffin Aromatization

    SciTech Connect

    Price, G.L.; Dooley, K.M.

    1999-02-10

    The primary original goal of this project was to investigate the active state of gallium-containing MFI catalysts for light paraffin aromatization, in particular the state of gallium in the active material. Our original hypothesis was that the most active and selective materials were those which contained gallium zeolitic cations, and that previously reported conditions for the activation of gallium-containing catalysts served to create these active centers. We believed that in high silica materials such as MFI, ion-exchange is most effectively accomplished with metals in their 1+ oxidation state, both because of the sparsity of the anionic ion-exchange sites associated with the zeolite, and because the large hydration shells associated with aqueous 3+ cations hinder transport. Metals such as Ga which commonly exist in higher oxidation states need to be reduced to promote ion-exchange and this is the reason that reduction of gallium-containing catalysts for light paraffin aromatization often yields a dramatic enhancement in catalytic activity. We have effectively combined reduction with ion-exchange and we term this combined process ''reductive solid-state ion-exchange''. Our hypothesis has largely been proven true, and a number of the papers we have published directly address this hypothesis.

  11. Single gallium nitride nanowire lasers.

    PubMed

    Johnson, Justin C; Choi, Heon-Jin; Knutsen, Kelly P; Schaller, Richard D; Yang, Peidong; Saykally, Richard J

    2002-10-01

    There is much current interest in the optical properties of semiconductor nanowires, because the cylindrical geometry and strong two-dimensional confinement of electrons, holes and photons make them particularly attractive as potential building blocks for nanoscale electronics and optoelectronic devices, including lasersand nonlinear optical frequency converters. Gallium nitride (GaN) is a wide-bandgap semiconductor of much practical interest, because it is widely used in electrically pumped ultraviolet-blue light-emitting diodes, lasers and photodetectors. Recent progress in microfabrication techniques has allowed stimulated emission to be observed from a variety of GaN microstructures and films. Here we report the observation of ultraviolet-blue laser action in single monocrystalline GaN nanowires, using both near-field and far-field optical microscopy to characterize the waveguide mode structure and spectral properties of the radiation at room temperature. The optical microscope images reveal radiation patterns that correlate with axial Fabry-Perot modes (Q approximately 10(3)) observed in the laser spectrum, which result from the cylindrical cavity geometry of the monocrystalline nanowires. A redshift that is strongly dependent on pump power (45 meV microJ x cm(-2)) supports the idea that the electron-hole plasma mechanism is primarily responsible for the gain at room temperature. This study is a considerable advance towards the realization of electron-injected, nanowire-based ultraviolet-blue coherent light sources. PMID:12618824

  12. Ambient temperature deposition of gallium nitride/gallium oxynitride from a deep eutectic electrolyte, under potential control.

    PubMed

    Sarkar, Sujoy; Sampath, S

    2016-05-11

    A ternary, ionically conducting, deep eutectic solvent based on acetamide, urea and gallium nitrate is reported for the electrodeposition of gallium nitride/gallium indium nitride under ambient conditions; blue and white light emitting photoluminescent deposits are obtained under potential control. PMID:27074315

  13. Gallium nitride as a material for spintronics

    NASA Astrophysics Data System (ADS)

    Khludkov, S. S.; Prudaev, I. A.; Тоlbanov, О. P.

    2013-01-01

    The literature on the magnetic properties of GaN doped with magnetic impurities: the transition metals (Mn, Cr, Fe, Ni, and V) and rare earth elements (Gd, Eu, and Sm), as well as gallium nitride containing high concentration of gallium vacancies and quantum dots is reviewed. The properties of GaN doped by ion implantation and during the MBE and MOVPE growth of layers are considered. The undoped GaN and GaN films doped with the transition metals and rare earth elements often retain ferromagnetic properties at room temperature.

  14. Radiation damage of gallium arsenide production cells

    NASA Technical Reports Server (NTRS)

    Mardesich, N.; Joslin, D.; Garlick, J.; Lillington, D.; Gillanders, M.; Cavicchi, B.; Scott-Monck, J.; Kachare, R.; Anspaugh, B.

    1987-01-01

    High efficiency liquid phase epitaxy (LPE) gallium arsenide cells were irradiated with 1 Mev electrons up to fluences of 1 times 10 to the 16th power cm-2. Measurements of spectral response and dark and illuminated I-V data were made at each fluence and then, using computer codes, the experimental data was fitted to gallium arsenide cell models. In this way it was possible to determine the extent of the damage, and hence damage coefficients in both the emitter and base of the cell.

  15. Gallium nitride-based micro-opto-electro-mechanical systems

    NASA Astrophysics Data System (ADS)

    Stonas, Andreas Robert

    Gallium Nitride and its associated alloys InGaN and AlGaN have many material properties that are highly desirable for micro-electro-mechanical systems (MEMS), and more specifically micro-opto-electro-mechanical systems (MOEMS). The group III-nitrides are tough, stiff, optically transparent, direct bandgap, chemically inert, highly piezoelectric, and capable of functioning at high temperatures. There is currently no other semiconductor system that possesses all of these properties. Taken together, these attributes make the nitrides prime candidates not only for creating new versions of existing device structures, but also for creating entirely unique devices which combine these properties in novel ways. Unfortunately, their chemical resiliency also makes the group III-nitrides extraordinarily difficult to shape into devices. In particular, until this research, no undercut etch technology existed that could controllably separate a selected part of a MEMS device from its sapphire or silicon carbide substrate. This has effectively prevented GaN-based MEMS from being developed. This dissertation describes how this fabrication obstacle was overcome by a novel etching geometry (bandgap-selective backside-illuminated photoelectochemical (BS-BIPEC) etching) and its resulting morphologies. Several gallium-nitride based MEMS devices were created, actuated, and modelled, including cantilevers and membranes. We describe in particular our pursuit of one of the many novel device elements that is possible only in this material system: a transducer that uses an externally applied strain to dynamically change the optical transition energy of a quantum well. While the device objective of a dynamically tunable quantum well was not achieved, we have demonstrated sufficient progress to believe that such a device will be possible soon. We have observed a shift (5.5meV) of quantum well transition energies in released structures, and we have created structures that can apply large biaxial stresses, which are required to produce significantly larger tuning (up to several hundred meV) in quantum well-based devices.

  16. Gallium vacancy complexes as a cause of Shockley-Read-Hall recombination in III-nitride light emitters

    NASA Astrophysics Data System (ADS)

    Dreyer, Cyrus E.; Alkauskas, Audrius; Lyons, John L.; Speck, James S.; Van de Walle, Chris G.

    2016-04-01

    We describe a mechanism by which complexes between gallium vacancies and oxygen and/or hydrogen act as efficient channels for nonradiative recombination in InGaN alloys. Our identification is based on first-principles calculations of defect formation energies, charge-state transition levels, and nonradiative capture coefficients for electrons and holes. The dependence of these quantities on alloy composition is analyzed. We find that modest concentrations of the proposed defect complexes (˜1016 cm-3) can give rise to Shockley-Read-Hall coefficients A =(107-109) s-1. The resulting nonradiative recombination would significantly reduce the internal quantum efficiency of optoelectronic devices.

  17. Synchrotron X-Ray Fluorescence Microscopy of Gallium in Bladder Tissue following Gallium Maltolate Administration during Urinary Tract Infection

    PubMed Central

    Sampieri, Francesca; Chirino, Manuel; Hamilton, Don L.; Blyth, Robert I. R.; Sham, Tsun-Kong; Dowling, Patricia M.; Thompson, Julie

    2013-01-01

    A mouse model of cystitis caused by uropathogenic Escherichia coli was used to study the distribution of gallium in bladder tissue following oral administration of gallium maltolate during urinary tract infection. The median concentration of gallium in homogenized bladder tissue from infected mice was 1.93 μg/g after daily administration of gallium maltolate for 5 days. Synchrotron X-ray fluorescence imaging and X-ray absorption spectroscopy of bladder sections confirmed that gallium arrived at the transitional epithelium, a potential site of uropathogenic E. coli infection. Gallium and iron were similarly but not identically distributed in the tissues, suggesting that at least some distribution mechanisms are not common between the two elements. The results of this study indicate that gallium maltolate may be a suitable candidate for further development as a novel antimicrobial therapy for urinary tract infections caused by uropathogenic E. coli. PMID:23877680

  18. Gallium Electromagnetic (GEM) Thruster Performance Measurements

    NASA Technical Reports Server (NTRS)

    Thomas, Robert E.; Burton, Rodney L.; Polzin, K. A.

    2009-01-01

    Discharge current, terminal voltage, and mass bit measurements are performed on a coaxial gallium electromagnetic thruster at discharge currents in the range of 7-23 kA. It is found that the mass bit varies quadratically with the discharge current which yields a constant exhaust velocity of 20 km/s. Increasing the electrode radius ratio of the thruster from to 2.6 to 3.4 increases the thruster efficiency from 21% to 30%. When operating with a central gallium anode, macroparticles are ejected at all energy levels tested. A central gallium cathode ejects macroparticles when the current density exceeds 3.7 10(exp 8) A/square m . A spatially and temporally broad spectroscopic survey in the 220-520 nm range is used to determine which species are present in the plasma. The spectra show that neutral, singly, and doubly ionized gallium species are present in the discharge, as well as annular electrode species at higher energy levels. Axial Langmuir triple probe measurements yield electron temperatures in the range of 0.8-3.8 eV and electron densities in the range of 8 x 10(exp )20 to 1.6 x 10(exp 21) m(exp -3) . Triple probe measurements suggest an exhaust plume with a divergence angle of 9 , and a completely doubly ionized plasma at the ablating thruster cathode.

  19. SPECT gallium imaging in abdominal lymphoma

    SciTech Connect

    Adcock, K.A.; Friefeld, G.D.; Waldron, J.A. Jr.

    1986-05-01

    A case of non-Hodgkin's lymphoma of the abdomen studied by gallium SPECT imaging is reported. The tomographic slices accurately demonstrated the location of residual disease after chemotherapy in the region of the transverse mesocolon. Previous transmission CT had shown considerable persistent retroperitoneal lymphadenopathy, but was not helpful in determining the presence of viable lymphoma.

  20. Gallium Nitride Crystals: Novel Supercapacitor Electrode Materials.

    PubMed

    Wang, Shouzhi; Zhang, Lei; Sun, Changlong; Shao, Yongliang; Wu, Yongzhong; Lv, Jiaxin; Hao, Xiaopeng

    2016-05-01

    A type of single-crystal gallium nitride mesoporous membrane is fabricated and its supercapacitor properties are demonstrated for the first time. The supercapacitors exhibit high-rate capability, stable cycling life at high rates, and ultrahigh power density. This study may expand the range of crystals as high-performance electrode materials in the field of energy storage. PMID:27007502

  1. 49 CFR 173.162 - Gallium.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... refrigeration. If a refrigerant is used, all of the above materials used in the packaging of gallium must be chemically and physically resistant to the refrigerant and must have impact resistance at the low temperatures of the refrigerant employed. If dry ice is used, the outer packaging must permit the release...

  2. 49 CFR 173.162 - Gallium.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... refrigeration. If a refrigerant is used, all of the above materials used in the packaging of gallium must be chemically and physically resistant to the refrigerant and must have impact resistance at the low temperatures of the refrigerant employed. If dry ice is used, the outer packaging must permit the release...

  3. Extrapulmonary localization of gallium in sarcoidosis

    SciTech Connect

    Rohatgi, P.K.; Singh, R.; Vieras, F.

    1987-01-01

    This paper describes the spectrum of extrapulmonary localization of gallium in patients with sarcoidosis. The usefulness of Ga-67 scintiscans in detecting clinically occult lesions, in directing clinicians to accessible sites for biopsy, and in following the course of extrapulmonary sites of involvement with therapy is emphasized.

  4. A Gallium Multiphase Equation of State

    NASA Astrophysics Data System (ADS)

    Crockett, Scott; Greeff, Carl

    2009-06-01

    A new SESAME multiphase gallium equation of state (EOS) has been developed. The equation of state includes two of the solid phases (Ga I, Ga III) and a fluid phase. The EOS includes consistent latent heat between the phases. We compare the results to the liquid Hugoniot data. We will also explore refreezing via isentropic release and compression.

  5. Solar cell with a gallium nitride electrode

    DOEpatents

    Pankove, Jacques I.

    1979-01-01

    A solar cell which comprises a body of silicon having a P-N junction therein with a transparent conducting N-type gallium nitride layer as an ohmic contact on the N-type side of the semiconductor exposed to solar radiation.

  6. Gallium-positive Lyme disease myocarditis

    SciTech Connect

    Alpert, L.I.; Welch, P.; Fisher, N.

    1985-09-01

    In the course of a work-up for fever of unknown origin associated with intermittent arrhythmias, a gallium scan was performed which revealed diffuse myocardial uptake. The diagnosis of Lyme disease myocarditis subsequently was confirmed by serologic titers. One month following recovery from the acute illness, the abnormal myocardial uptake completely resolved.

  7. Gallium nitride junction field-effect transistor

    DOEpatents

    Zolper, John C.; Shul, Randy J.

    1999-01-01

    An all-ion implanted gallium-nitride (GaN) junction field-effect transistor (JFET) and method of making the same. Also disclosed are various ion implants, both n- and p-type, together with or without phosphorous co-implantation, in selected III-V semiconductor materials.

  8. Gallium nitride junction field-effect transistor

    DOEpatents

    Zolper, J.C.; Shul, R.J.

    1999-02-02

    An ion implanted gallium-nitride (GaN) junction field-effect transistor (JFET) and method of making the same are disclosed. Also disclosed are various ion implants, both n- and p-type, together with or without phosphorus co-implantation, in selected III-V semiconductor materials. 19 figs.

  9. Anisotropy of the magnetic susceptibility of gallium

    USGS Publications Warehouse

    Pankey, T., Jr.

    1960-01-01

    The bulk magnetic susceptibilities of single gallium crystals and polycrystalline gallium spheres were measured at 25??C. The following anisotropic diamagnetic susceptibilities were found: a axis (-0.119??0. 001)??10-6 emu/g, b axis (-0.416??0.002)??10 -6 emu/g, and c axis (-0.229??0.001) emu/g. The susceptibility of the polycrystalline spheres, assumed to be the average value for the bulk susceptibility of gallium, was (-0.257??0.003)??10-6 emu/g at 25??C, and (-0.299??0.003)??10-6 emu/g at -196??C. The susceptibility of liquid gallium was (0.0031??0.001) ??10-6 emu/g at 30??C and 100??C. Rotational diagrams of the susceptibilities in the three orthogonal planes of the unit cell were not sinusoidal. The anisotropy in the single crystals was presumably caused by the partial overlap of Brillouin zone boundaries by the Fermi-energy surface. The large change in susceptibility associated with the change in state was attributed to the absence of effective mass influence in the liquid state. ?? 1960 The American Institute of Physics.

  10. Gallium 67 scintigraphy in glomerular disease

    SciTech Connect

    Bakir, A.A.; Lopez-Majano, V.; Levy, P.S.; Rhee, H.L.; Dunea, G.

    1988-12-01

    To evaluate the diagnostic usefulness of gallium 67 scintigraphy in glomerular disease, 45 patients with various glomerulopathies, excluding lupus nephritis and renal vasculitis, were studied. Persistent renal visualization 48 hours after the gallium injection, a positive scintigram, was graded as + (less than), ++ (equal to), and +++ (greater than) the hepatic uptake. Positive scintigrams were seen in ten of 16 cases of focal segmental glomerulosclerosis, six of 11 cases of proliferative glomerulonephritis, and one case of minimal change, and one of two cases of membranous nephropathy; also in three of six cases of sickle glomerulopathy, two cases of diabetic neuropathy, one of two cases of amyloidosis, and one case of mild chronic allograft rejection. The 25 patients with positive scans were younger than the 20 with negative scans (31 +/- 12 v 42 +/- 17 years; P less than 0.01), and exhibited greater proteinuria (8.19 +/- 7.96 v 2.9 +/- 2.3 S/d; P less than 0.01) and lower serum creatinine values (2 +/- 2 v 4.1 +/- 2.8 mg/dL; P less than 0.01). The amount of proteinuria correlated directly with the intensity grade of the gallium image (P less than 0.02), but there was no correlation between the biopsy diagnosis and the outcome of the gallium scan. It was concluded that gallium scintigraphy is not useful in the differential diagnosis of the glomerular diseases under discussion. Younger patients with good renal function and heavy proteinuria are likely to have a positive renal scintigram regardless of the underlying glomerulopathy.

  11. Palladium alloys for biomedical devices.

    PubMed

    Wataha, John C; Shor, Kavita

    2010-07-01

    In the biomedical field, palladium has primarily been used as a component of alloys for dental prostheses. However, recent research has shown the utility of palladium alloys for devices such as vascular stents that do not distort magnetic resonance images. Dental palladium alloys may contain minor or major percentages of palladium. As a minor constituent, palladium hardens, strengthens and increases the melting range of alloys. Alloys that contain palladium as the major component also contain copper, gallium and sometimes tin to produce strong alloys with high stiffness and relatively low corrosion rates. All current evidence suggests that palladium alloys are safe, despite fears about harmful effects of low-level corrosion products during biomedical use. Recent evidence suggests that palladium poses fewer biological risks than other elements, such as nickel or silver. Hypersensitivity to palladium alone is rare, but accompanies nickel hypersensitivity 90-100% of the time. The unstable price of palladium continues to influence the use of palladium alloys in biomedicine. PMID:20583886

  12. Serum and tissue concentrations of gallium after oral administration of gallium nitrate and gallium maltolate to neonatal calves.

    PubMed

    Monk, Caroline S; Sweeney, Raymond W; Bernstein, Lawrence R; Fecteau, Marie-Eve

    2016-02-01

    OBJECTIVE To determine serum and tissue concentrations of gallium (Ga) after oral administration of gallium nitrate (GaN) and gallium maltolate (GaM) to neonatal calves. ANIMALS 8 healthy neonatal calves. PROCEDURES Calves were assigned to 1 of 2 groups (4 calves/group). Gallium (50 mg/kg) was administered as GaN or GaM (equivalent to 13.15 mg of Ga/kg for GaN and 7.85 mg of Ga/kg for GaM) by oral gavage once daily for 5 days. Blood samples were collected 0, 0.25, 0.5, 1, 2, 4, 8, 12, and 24 hours after Ga administration on day 1; 4 and 24 hours after Ga administration on days 2, 3, and 4; and 4, 12, and 24 hours after Ga administration on day 5. On day 6, calves were euthanized and tissue samples were obtained. Serum and tissue Ga concentrations were measured by use of mass spectrometry. RESULTS Data were adjusted for total Ga dose, and comparisons were made between the 2 groups. Calves receiving GaM had a significantly higher dose-adjusted area under the curve and dose-adjusted maximum serum Ga concentration than did calves receiving GaN. Despite receiving less Ga per dose, calves receiving GaM had tissue Ga concentrations similar to those for calves receiving GaN. CONCLUSIONS AND CLINICAL RELEVANCE In this study, calves receiving GaM had significantly higher Ga absorption than did calves receiving GaN. These findings suggested that GaM might be useful as a prophylactic agent against Mycobacterium avium subsp paratuberculosis infection in neonatal calves. (Am J Vet Res 2016;77:151-155). PMID:27027708

  13. Light Elements in the Core: Constraints from Gallium Partitioning

    NASA Astrophysics Data System (ADS)

    Blanchard, I.; Badro, J.; Siebert, J.; Ryerson, F. J.

    2014-12-01

    The formation of Earth's core has left a compositional imprint on the mantle, depleting and fractionating most of its siderophile (iron-loving) elements. Gallium is a moderately siderophile, hence it should be strongly depleted in the mantle. However, gallium concentration in the mantle matches that of lithophile (silicate-loving) elements having the same volatility. That is to say that either gallium behaves as a lithophile element during core formation, or a large influx of gallium was brought to the Earth after the core had formed. Geochemical evidence does not support the latter hypothesis, as it would require all other lithophile elements with similar volatility to be enriched in the mantle, or for late accretion to be composed of anomalously gallium-rich objects. In order to mitigate this issue, experimental studies have tried to understand how gallium behaves during core segregation by gauging the effects of pressure, temperature and oxygen fugacity on the partitioning of gallium between metal and silicate. None of these parameters provided the first-order change required to match the observation. We investigated the influence of core composition on gallium partitioning. The core in known to contain light-elements (oxygen, silicon sulfur and carbon), and those can change the activity of gallium in the metal, and strongly affect the behavior of gallium during core formation. We performed a series of metal-silicate partitioning experiments (2 GPa, 1673-2073 K) in a piston-cylinder press. We varied the light-element composition of the metal and observed that Si and O have a very strong influence on the activity of gallium, making it more lithophile. We then modeled terrestrial accretion as a continuous process and tested different accretion histories; we can reproduce the mantle concentration of gallium if the core segregates in a deep magma ocean (>40 GPa) and contains large amounts of silicon or oxygen.

  14. Inflammatory pseudotumor: A gallium-avid mobile mesenteric mass

    SciTech Connect

    Auringer, S.T.; Scott, M.D.; Sumner, T.E. )

    1991-08-01

    An 8-yr-old boy with a 1-mo history of culture-negative fever and anemia underwent gallium, ultrasound, and computed tomography studies as part of the evaluation of a fever of unknown origin. These studies revealed a mobile gallium-avid solid abdominal mass subsequently proven to be an inflammatory pseudotumor of the mesentery, a rare benign mass. This report documents the gallium-avid nature of this rare lesion and discusses associated characteristic clinical, pathologic, and radiographic features.

  15. Corrosion development between liquid gallium and four typical metal substrates used in chip cooling device

    NASA Astrophysics Data System (ADS)

    Deng, Yue-Guang; Liu, Jing

    2009-06-01

    The limitation of the currently available thermal management method has put an ever serious challenge for computer chip designers. A liquid metal with low melting point around room temperature was recently identified as a powerful coolant of driving heat away because of its superior thermo-physical properties and the unique ability to be driven efficiently by a completely silent electromagnetic pump. However, the adoption of gallium, one of the best candidates as metal coolant so far, may cause serious corrosion to the structure materials and subsequently affect the performance or even dangerous running of the cooling system. To address this emerging critical issue, here the compatibility of gallium with four typical metal substrates (6063 Aluminum-Alloy, T2 Copper-Alloy, Anodic Coloring 6063 Aluminum-Alloy and 1Cr18Ni9 Stainless Steel) was comprehensively investigated in order to better understand the corrosion mechanisms and help find out the most suitable structure material for making a liquid metal cooling device. To grasp in detail the dynamic corrosion behavior, an image acquisition and contrasting method was developed. Moreover, corrosion morphology analyses were performed by means of scanning electron microscope (SEM). The chemical compositions of the corroded layers were evaluated using energy dispersive spectrometry (EDS). According to the experiments, it was found that, the corrosion of the 6063 Aluminum-Alloy was rather evident and serious under the temperature range for chip cooling. The loose corrosion product will not only have no protection for the inner substrate, but also accelerate the corrosion process. Compared to the 6063 Aluminum-Alloy, T2 Copper-Alloy showed a slow and general corrosion, but part of the corrosion product can shed from the substrate, which will accelerate corrosion action and may block the flowing channel. Anodic Coloring 6063 Aluminum-Alloy and 1Cr18Ni9 Stainless Steel were found to have excellent corrosion resistance among these four specimens. No evident corrosion phenomena were found under the examination of SEM and EDS when exposed for 30 days at the temperature of 60°C, which suggests their suitability as structure materials for the flow of liquid metal. However, as for the Anodic Coloring 6063 Aluminum-Alloy, surface treatment and protection are of vital importance. The present study is of significance for making a liquid metal chip cooling device which can actually be used in the future computer industry.

  16. Optical properties and plasmonic response of silver-gallium nanostructures

    NASA Astrophysics Data System (ADS)

    Lereu, A. L.; Lemarchand, F.; Zerrad, M.; Yazdanpanah, M.; Passian, A.

    2015-02-01

    Silver and gallium form an alloy Ag2Ga via a room temperature spontaneous self-assembly that exhibits remarkable mechanical and electrical properties suitable for nanoscale measurements. However, whether photon excitation of plasmons in this emerging nanomaterial is retained or not has not been established. Here, we present a thin film formation of Ag2Ga via a spreading-reactive process of liquid Ga on an Ag film and a characterization of its dielectric function ɛ(E) = ɛ1(E) + iɛ2(E) in the photon energy range 1.42 eV ≤ E < 4.2 eV. It is observed that while the plasmon damping increases, near an energy of 2.25 eV, the real part of ɛ exhibits a crossing with respect to that of Ag. Furthermore, the impact of new plasmon supporting materials is discussed and in order to enable further applications in plasmonics, the possibility of photon excitation of surface plasmons in Ag2Ga is studied.

  17. Optical properties and plasmonic response of silver-gallium nanostructures

    SciTech Connect

    Lereu, A. L.; Lemarchand, F.; Zerrad, M.; Yazdanpanah, M.; Passian, A.

    2015-02-14

    Silver and gallium form an alloy Ag{sub 2}Ga via a room temperature spontaneous self-assembly that exhibits remarkable mechanical and electrical properties suitable for nanoscale measurements. However, whether photon excitation of plasmons in this emerging nanomaterial is retained or not has not been established. Here, we present a thin film formation of Ag{sub 2}Ga via a spreading-reactive process of liquid Ga on an Ag film and a characterization of its dielectric function ϵ(E) = ϵ{sub 1}(E) + iϵ{sub 2}(E) in the photon energy range 1.42 eV ≤ E < 4.2 eV. It is observed that while the plasmon damping increases, near an energy of 2.25 eV, the real part of ϵ exhibits a crossing with respect to that of Ag. Furthermore, the impact of new plasmon supporting materials is discussed and in order to enable further applications in plasmonics, the possibility of photon excitation of surface plasmons in Ag{sub 2}Ga is studied.

  18. Efficient water reduction with gallium phosphide nanowires.

    PubMed

    Standing, Anthony; Assali, Simone; Gao, Lu; Verheijen, Marcel A; van Dam, Dick; Cui, Yingchao; Notten, Peter H L; Haverkort, Jos E M; Bakkers, Erik P A M

    2015-01-01

    Photoelectrochemical hydrogen production from solar energy and water offers a clean and sustainable fuel option for the future. Planar III/V material systems have shown the highest efficiencies, but are expensive. By moving to the nanowire regime the demand on material quantity is reduced, and new materials can be uncovered, such as wurtzite gallium phosphide, featuring a direct bandgap. This is one of the few materials combining large solar light absorption and (close to) ideal band-edge positions for full water splitting. Here we report the photoelectrochemical reduction of water, on a p-type wurtzite gallium phosphide nanowire photocathode. By modifying geometry to reduce electrical resistance and enhance optical absorption, and modifying the surface with a multistep platinum deposition, high current densities and open circuit potentials were achieved. Our results demonstrate the capabilities of this material, even when used in such low quantities, as in nanowires. PMID:26183949

  19. Efficient water reduction with gallium phosphide nanowires

    PubMed Central

    Standing, Anthony; Assali, Simone; Gao, Lu; Verheijen, Marcel A.; van Dam, Dick; Cui, Yingchao; Notten, Peter H. L.; Haverkort, Jos E. M.; Bakkers, Erik P. A. M.

    2015-01-01

    Photoelectrochemical hydrogen production from solar energy and water offers a clean and sustainable fuel option for the future. Planar III/V material systems have shown the highest efficiencies, but are expensive. By moving to the nanowire regime the demand on material quantity is reduced, and new materials can be uncovered, such as wurtzite gallium phosphide, featuring a direct bandgap. This is one of the few materials combining large solar light absorption and (close to) ideal band-edge positions for full water splitting. Here we report the photoelectrochemical reduction of water, on a p-type wurtzite gallium phosphide nanowire photocathode. By modifying geometry to reduce electrical resistance and enhance optical absorption, and modifying the surface with a multistep platinum deposition, high current densities and open circuit potentials were achieved. Our results demonstrate the capabilities of this material, even when used in such low quantities, as in nanowires. PMID:26183949

  20. Efficient water reduction with gallium phosphide nanowires

    NASA Astrophysics Data System (ADS)

    Standing, Anthony; Assali, Simone; Gao, Lu; Verheijen, Marcel A.; van Dam, Dick; Cui, Yingchao; Notten, Peter H. L.; Haverkort, Jos E. M.; Bakkers, Erik P. A. M.

    2015-07-01

    Photoelectrochemical hydrogen production from solar energy and water offers a clean and sustainable fuel option for the future. Planar III/V material systems have shown the highest efficiencies, but are expensive. By moving to the nanowire regime the demand on material quantity is reduced, and new materials can be uncovered, such as wurtzite gallium phosphide, featuring a direct bandgap. This is one of the few materials combining large solar light absorption and (close to) ideal band-edge positions for full water splitting. Here we report the photoelectrochemical reduction of water, on a p-type wurtzite gallium phosphide nanowire photocathode. By modifying geometry to reduce electrical resistance and enhance optical absorption, and modifying the surface with a multistep platinum deposition, high current densities and open circuit potentials were achieved. Our results demonstrate the capabilities of this material, even when used in such low quantities, as in nanowires.

  1. Positive gallium scan in retroperitoneal fibrosis

    SciTech Connect

    Liebman, R.M.

    1983-11-01

    Many articles have described the computed tomographic (CT) diagnosis of retroperitoneal fibrosis and its similarities to lymphoma and other retroperitoneal processes. The author reports a patient with classic uroradiographic findings of retroperitoneal fibrosis and CT findings consistent with extensive periaortic masses. A gallium-67 (/sup 67/Ga) citrate scan, performed to exclude lymphoma, demonstrated intense periaortic activity. Specimens obtained during laparotomy, however, showed typical pathologic findings of retroperitoneal fibrosis without evidence of lymphoma or other malignancies.

  2. Gallium-67 imaging in muscular sarcoidosis

    SciTech Connect

    Edan, G.; Bourguet, P.; Delaval, P.; Herry, J.Y.

    1984-07-01

    A case is presented of sarcoid myopathy in which radiogallium was seen to accumulate in the sites of muscle involvement. Uptake of the radiotracer disappeared following institution of corticosteroid therapy. The exceptional nature of this case contrasts with the high frequency of biopsy evidence of sarcoid granulomas in muscle. Gallium-67 imaging can be used to determine the extent of muscle involvement and, through evaluation of uptake intensity, the degree of disease activity before and after treatment.

  3. a Gallium Multiphase Equation of State

    NASA Astrophysics Data System (ADS)

    Crockett, Scott D.; Greeff, Carl W.

    2009-12-01

    A new SESAME multiphase Gallium equation of state (EOS) has been developed. It includes three of the solid phases (Ga I, Ga II, Ga III) and a fluid phase (liquid/gas). The EOS includes consistent latent heat between the phases. We compare the results to the liquid Hugoniot data. We also explore the possibility of re-freezing via dynamic means such as isentropic and shock compression. We predict an unusual spontaneous spreading of low pressure shocks from STP.

  4. A Gallium multiphase equation of state

    SciTech Connect

    Crockett, Scott D; Greeff, Carl

    2009-01-01

    A new SESAME multiphase Gallium equation of state (EOS) has been developed. The equation of state includes three of the solid phases (Ga I, Ga II, Ga III) and a fluid phase (liquid/gas). The EOS includes consistent latent heat between the phases. We compare the results to the liquid Hugoniol data. We also explore the possibility of re-freezing via dynamic means such as isentropic and shock compression.

  5. GaN growth using gallium hydride generated by hydrogenation of liquid gallium

    NASA Astrophysics Data System (ADS)

    Nagayoshi, H.; Nishimura, S.; Takeuchi, T.; Hirai, M.; Terashima, K.

    2005-02-01

    The novel growth method of GaN using hydrogen radicals has been investigated. This paper is the first report of gallium hydrogenation reaction and deposition of GaN using hydrogenated gallium. We found that gallium (Ga) could be volatilized at low temperature by hydrogenation reaction with hydrogen radicals. In this reaction, Ga assumed to be volatilized as GaH 3. The GaN deposition was attempted by using gas phase reaction of NH 3 and GaH 3 generated by the reaction between liquid Ga and hydrogen radicals. Hydrogen radicals were generated by hot tungsten filament, which works as a catalyst during hydrogen cracking, whose temperature was 1600 °C. Surface morphology, deposition rate, and film structure were investigated. It was confirmed that GaN could be deposited by this method. The source materials of this method are safe and of low cost compared to the conventional methods.

  6. Scanning probe microscopy on new dental alloys

    NASA Astrophysics Data System (ADS)

    Reusch, B.; Geis-Gerstorfer, J.; Ziegler, C.

    Surface analytical methods such as scanning force microscopy (SFM), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were used to determine the surface properties of amalgam substitutes as tooth filling materials. In particular the corrosion and the passivation behavior of new gallium restorative materials were studied. To give relevant practical data, the measurements were performed with and without the alloys being stored in artificial saliva to simulate physiological oral conditions.

  7. Gallium arsenide for devices and integrated circuits

    SciTech Connect

    Morgan, D.V.; Thomas, H.

    1986-01-01

    Gallium Arsenide has long been hailed as the material of the future and it is only in recent years that the technology associated with its growth and processing has matured to the point where IC production can be contemplated at the industrial level. This point has now been reached and the electronics industries in Europe, the USA and Japan are actively moving from research activities into product development using this and related material. The text is divided into 15 chapters: Gallium Arsenide: Physical and Transport Properties; Liquid phase and Vapour Phase Epitaxy of GaAs and Related Compounds; Expitaxial Growth and GaAs: MBE and MOCVD; Characterization of GaAs I: Electrical Techniques; Characterization of GaAsII: Ion Beam Analysis; Ion Implantation; Wet and Dry Processing GaAs; Microwave and Millimetre - Wave Diodes; GaAs Mesfet's and High Electron Mobility Transistors (HEMT); Optoelectronic Devices and Components; Gallium Arsenide Monolithic Microwave Integrated Circuits; GaAs Digital Integrated Circuits; III-V Semiconductors for Solar Cells.

  8. Automated realization of the gallium melting and triple points

    NASA Astrophysics Data System (ADS)

    Yan, X.; Duan, Y.; Zhang, J. T.; Wang, W.

    2013-09-01

    In order to improve the automation and convenience of the process involved in realizing the gallium fixed points, an automated apparatus, based on thermoelectric and heat pipe technologies, was designed and developed. This paper describes the apparatus design and procedures for freezing gallium mantles and realizing gallium melting and triple points. Also, investigations on the melting behavior of a gallium melting point cell and of gallium triple point cells were carried out while controlling the temperature outside the gallium point cells at 30 °C, 30.5 °C, 31 °C, and 31.5 °C. The obtained melting plateau curves show dentate temperature oscillations on the melting plateaus for the gallium point cells when thermal couplings occurred between the outer and inner liquid-solid interfaces. The maximum amplitude of the temperature fluctuations was about 1.5 mK. Therefore, the temperature oscillations can be used to indicate the ending of the equilibrium phase transitions. The duration and amplitude of such temperature oscillations depend on the temperature difference between the setting temperature and the gallium point temperature; the smaller the temperature difference, the longer the duration of both the melting plateaus and the temperature fluctuations.

  9. Studies on the reliability of ni-gate aluminum gallium nitride / gallium nitride high electron mobility transistors using chemical deprocessing

    NASA Astrophysics Data System (ADS)

    Whiting, Patrick Guzek

    Aluminum Gallium Nitride / Gallium Nitride High Electron Mobility Transistors are becoming the technology of choice for applications where hundreds of volts need to be applied in a circuit at frequencies in the hundreds of gigahertz, such as microwave communications. However, because these devices are very new, their reliability in the field is not well understood, partly because of the stochastic nature of the defects which form as a result of their operation. Many analytical techniques are not well suited to the analysis of these defects because they sample regions of the device which are either too small or too large for accurate observation. The use of chemical deprocessing in addition to surface-sensitive analysis techniques such as Scanning Electron Microscopy and Scanning Probe Microscopy can be utilized in the analysis of defect formation in devices formed with nickel gates. Hydrofluoric acid is used to etch the passivation nitride which covers the semiconducting layer of the transistor. A metal etch utilizing FeCN/KI is used to etch the ohmic and gate contacts of the device and a long exposure in various solvent solutions is used to remove organic contaminants, exposing the surface of the semiconducting layer for analysis. Deprocessing was used in conjunction with a variety of metrology techniques to analyze three different defects. One of these defects is a nanoscale crack which emanates from metal inclusions formed during alloying of the ohmic contacts of the device prior to use in the field, could impact the yield of production-level manufacturing of these devices. This defect also appears to grow, in some cases, during electrostatic stressing. Another defect, a native oxide at the surface of the semiconducting layer which appears to react in the presence of an electric field, has not been observed before during post-mortem analysis of degraded devices. It could play a major part in the degredation of the gate contact during high-field, off-mode electrostatic stressing and could be the initiator of the pitting of the semiconducting layer of the gate contact, a defect which was also observed.

  10. Nuclear microprobe imaging of gallium nitrate in cancer cells

    NASA Astrophysics Data System (ADS)

    Ortega, Richard; Suda, Asami; Devès, Guillaume

    2003-09-01

    Gallium nitrate is used in clinical oncology as treatment for hypercalcemia and for cancer that has spread to the bone. Its mechanism of antitumor action has not been fully elucidated yet. The knowledge of the intracellular distribution of anticancer drugs is of particular interest in oncology to better understand their cellular pharmacology. In addition, most metal-based anticancer compounds interact with endogenous trace elements in cells, altering their metabolism. The purpose of this experiment was to examine, by use of nuclear microprobe analysis, the cellular distribution of gallium and endogenous trace elements within cancer cells exposed to gallium nitrate. In a majority of cellular analyses, gallium was found homogeneously distributed in cells following the distribution of carbon. In a smaller number of cells, however, gallium appeared concentrated together with P, Ca and Fe within round structures of about 2-5 μm diameter located in the perinuclear region. These intracellular structures are typical of lysosomial material.

  11. Calcium - niobium - gallium and calcium - lithium - niobium - gallium garnet crystals as active media for diode-pumped lasers

    SciTech Connect

    Voronko, Yu K; Es'kov, N A; Podstavkin, A S; Ryabochkina, P A; Sobol, A A; Ushakov, S N

    2001-06-30

    The energy and spectral parameters of calcium - niobium - gallium and calcium - lithium - niobium - gallium garnet crystals pumped by a 2 - W laser diode are studied. The stable parameters of laser radiation are demonstrated upon small variations in the temperature of the pump laser diode. (lasers, active media)

  12. Gallium scintigraphic pattern in lung CMV infections

    SciTech Connect

    Ganz, W.I.; Cohen, D.; Mallin, W.

    1994-05-01

    Due to extensive use of prophylactic therapy for Pneumonitis Carinii Pneumonia (PCP), Cytomegalic Viral (CMV) infection may now be the most common lung infection in AIDS patients. This study was performed to determine Gallium-67 patterns in AIDS patients with CMV. Pathology reports were reviewed in AIDS patients who had a dose of 5 to 10 mCi of Gallium-67 citrate. Analysis of images were obtained 48-72 hours later of the entire body was performed. Gallium-67 scans in 14 AIDS patients with biopsy proven CMV, were evaluated for eye, colon, adrenal, lung and renal uptake. These were compared to 40 AIDS patients without CMV. These controls had infections including PCP, Mycobacterial infections, and lymphocytic interstitial pneumonitis. 100% of CMV patients had bowel uptake greater than or equal to liver. Similar bowel activity was seen in 50% of AIDS patients without CMV. 71% had intense eye uptake which was seen in only 10% of patients without CMV. 50% of CMV patients had renal uptake compared to 5% of non-CMV cases. Adrenal uptake was suggested in 50%, however, SPECT imaging is needed for confirmation. 85% had low grade lung uptake. The low grade lung had perihilar prominence. The remaining 15% had high grade lung uptake (greater than sternum) due to superimposed PCP infection. Colon uptake is very sensitive indicator for CMV infection. However, observing eye, renal, and or adrenal uptake improved the diagnostic specificity. SPECT imaging is needed to confirm renal or adrenal abnormalities due to intense bowel activity present in 100% of cases. When high grade lung uptake is seen superimposed PCP is suggested.

  13. The Preparation and Structural Characterization of Three Structural Types of Gallium Compounds Derived from Gallium (II) Chloride

    NASA Technical Reports Server (NTRS)

    Gordon, Edward M.; Hepp, Aloysius F.; Duraj. Stan A.; Habash, Tuhfeh S.; Fanwick, Phillip E.; Schupp, John D.; Eckles, William E.; Long, Shawn

    1997-01-01

    The three compounds Ga2Cl4(4-mepy)2 (1),[GaCl2(4-mepy)4]GaCl4x1/2(4-mepy); (2) and GaCl2(4-mepy)2(S2CNEt2); (3) (4-mepy= 4-methylpyridine) have been prepared from reactions of gallium (II) chloride in 4-methylpyridine and characterized by single-crystal X-ray analysis. Small variations in the reaction conditions for gallium(II) chloride can produce crystals with substantially different structural properties. The three compounds described here encompass a neutral gallium(II) dimer in which each gallium is four-coordinate, an ionic compound containing both anionic and cationic gallium complex ions with different coordination numbers and a neutral six-coordinate heteroleptic

  14. Gallium-67 imaging in muscular sarcoidosis

    SciTech Connect

    Edan, G.; Bourguet, P.; Delaval, P.; Herry, J.Y.

    1984-07-01

    A case is presented of sarcoid myopathy in which radiogallium was seen to accumulate in the sites of muscle involvement. Uptake of the radiotracer disappeared following institution of corticosteroid therapy. The exceptional nature of this case contrasts with the high frequency of biopsy evidence of sarcoid muscle disease but is consistent with the rarity of clinical evidence of sarcoid granulomas in muscle. Gallium-67 imaging can be used to determine the extent of muscle involvement and, through evaluation of uptake intensity, the degree of disease activity before and after treatment.

  15. Gallium increases bone calcium and crystallite perfection of hydroxyapatite.

    PubMed

    Bockman, R S; Boskey, A L; Blumenthal, N C; Alcock, N W; Warrell, R P

    1986-12-01

    Gallium, a group IIIa metal, is known to interact with hydroxyapatite as well as the cellular components of bone. In recent studies we have found gallium to be a potent inhibitor of bone resorption that is clinically effective in controlling cancer-related hypercalcemia as well as the accelerated bone resorption associated with bone metastases. To begin to elucidate gallium's mechanism of action we have examined its effects on bone mineral properties. After short-term (14 days) administration to rats, gallium nitrate produced measurable changes in bone mineral properties. Using atomic absorption spectroscopy, low levels of gallium were noted to preferentially accumulate in regions of active bone formation, 0.54 +/- .07 microgram/mg bone in the metaphyses versus 0.21 +/- .03 microgram/mg bone in the diaphyses, P less than 0.001. The bones of treated animals had increased calcium content measured spectrophotometrically. Rats injected with radiolabeled calcium during gallium treatment had greater 45-calcium content compared to control animals. By wide-angle X-ray analyses, larger and/or more perfect hydroxyapatite was observed. The combined effects of gallium on bone cell function and bone mineral may explain its clinical efficacy in blocking accelerated bone resorption. PMID:3026592

  16. Behavior of Zircaloy Cladding in the Presence of Gallium

    SciTech Connect

    DiStefano, J.R.; King, J.F.; Manneschmidt, E.T.; Strizak, J.P.; Wilson, D.F.

    1998-09-28

    The U.S. Department of Energy has established a dual-track approach to the disposition of plutonium arising from the dismantling of nuclear weapons. Both immobilization and reactor-based mixed-oxide (MOX) fuel technologies are being evaluated. The reactor-based MOX fuel option requires assessment of the potential impact of concentrations of gallium (on the order of 1 to 10 ppm), not present in conventional MOX fuel, on cladding material performance. An experimental program was designed to evaluate the performance of prototypic Zircaloy cladding materials against (1) liquid gallium, and (2) various concentrations of G~03. Three types of tests were performed: (1) corrosion, (2) liquid metal embrittlement, and (3) corrosion-mechanical. These tests were to determine corrosion mechanisms, thresholds for temperature and concentration of gallium that delineate behavioral regimes, and changes in the mechanical properties of Zircaloy. Results have generally been favorable for the use of weapons-grade (WG) MOX fhel. The Zircaloy cladding does react with gallium to form intermetallic compounds at >3000 C; however, this reaction is limited by the mass of gallium and is therefore not expected to be significant with a low level (parts per million) of gallium in the MOX fuel. Furthermore, no evidence for grain boundary penetration by gallium or liquid metal embrittlement was observed.

  17. Assessment of gallium-67 scanning in pulmonary and extrapulmonary sarcoidosis

    SciTech Connect

    Israel, H.L.; Gushue, G.F.; Park, C.H.

    1986-01-01

    Gallium-67 scans have been widely employed in patients with sarcoidosis as a means of indicating alveolitis and the need for corticosteroid therapy. Observation of 32 patients followed 3 or more years after gallium scans showed no correlation between findings and later course: of 10 patients with pulmonary uptake, 7 recovered with minor residuals; of 18 patients with mediastinal of extrathoracic uptake, 10 had persistent or progressive disease; of 4 patients with negative initial scans, 2 had later progression. The value of gallium-67 scans as an aid to diagnosis was studied in 40 patients with extrapulmonary sarcoidosis. In 12 patients, abnormal lacrimal, nodal, or pulmonary uptake aided in selection of biopsy sites. Gallium-67 scans and serum ACE levels were compared in 97 patients as indices of clinical activity. Abnormal gallium-67 uptake was observed in 96.3% of the tests in active disease, and ACE level elevation occurred in 56.3%. In 24 patients with inactive or recovered disease, abnormal gallium-67 uptake occurred in 62.5% and ACE level elevation in 37.5%. Gallium-67 scans have a limited but valuable role in the diagnosis and management of sarcoidosis.

  18. Dispersion of submicron Ni particles into liquid gallium

    NASA Astrophysics Data System (ADS)

    Cao, L. F.; Park, H. S.; Dodbiba, G.; Fujita, T.

    2008-06-01

    In this paper a liquid gallium with a low melting temperature and good thermal conductivity was used as a carrier to develop a new magnetorheological (MR) fluid that can be employed in energy convection devices. Submicron nickel particles, coated with silica, were chosen to be dispersed in the liquid gallium. The silica coating was used to improve the dispersion and prepare the composite particles with a density similar to that of the carrier liquid, i.e., liquid gallium. The supercooling phenomenon of liquid gallium was analyzed to better understand the dispersion of particles. The magnetization behaviours of both the silica-coated nickel particles and the synthesized MR fluids were measured. The results showed that the silica-coated nickel particles exhibited a shell-type structure, and the composite particle with a density same as the one of liquid gallium can be obtained by controlling the thickness of the coating layer to approximately 22 nm. The submicron nickel particles with the help of silica coating can be easily dispersed into liquid gallium. It was found that the supercooling of liquid gallium varied from 13.5 K to 19.3 K depending on the thickness of the coating layer of the dispersed particles. The saturation magnetization of the composite particles was reduced due to the occurrence of a non-magnetic silica layer. Figs 5, Refs 14.

  19. Gallium induces the production of virulence factors in Pseudomonas aeruginosa.

    PubMed

    García-Contreras, Rodolfo; Pérez-Eretza, Berenice; Lira-Silva, Elizabeth; Jasso-Chávez, Ricardo; Coria-Jiménez, Rafael; Rangel-Vega, Adrián; Maeda, Toshinari; Wood, Thomas K

    2014-02-01

    The novel antimicrobial gallium is a nonredox iron III analogue with bacteriostatic and bactericidal properties, effective for the treatment of Pseudomonas aeruginosa in vitro and in vivo in mouse and rabbit infection models. It interferes with iron metabolism, transport, and presumably its homeostasis. As gallium exerts its antimicrobial effects by competing with iron, we hypothesized that it ultimately will lead cells to an iron deficiency status. As iron deficiency promotes the expression of virulence factors in vitro and promotes the pathogenicity of P. aeruginosa in animal models, it is anticipated that treatment with gallium will also promote the production of virulence factors. To test this hypothesis, the reference strain PA14 and two clinical isolates from patients with cystic fibrosis were exposed to gallium, and their production of pyocyanin, rhamnolipids, elastase, alkaline protease, alginate, pyoverdine, and biofilm was determined. Gallium treatment induced the production of all the virulence factors tested in the three strains except for pyoverdine. In addition, as the Ga-induced virulence factors are quorum sensing controlled, co-administration of Ga and the quorum quencher brominated furanone C-30 was assayed, and it was found that C-30 alleviated growth inhibition from gallium. Hence, adding both C-30 and gallium may be more effective in the treatment of P. aeruginosa infections. PMID:24151196

  20. Numerical Simulation of Rotating Gallium Disk

    NASA Astrophysics Data System (ADS)

    Kageyama, Akira

    2001-10-01

    Laboratory experiment to study magnetorotational instability (MRI) using liquid gallium has been proposed at Princeton Plasma Physics Laboratory. In this experiment, liquid gallium in cylindrical annulus is subject to a rotating shear motion induced by a differential rotation of two (inner and outer) cylindrical walls. A magnetic field, parallel to the cylinders axis, is imposed and the MRI can be detected as a sudden breaking of rotating shear motion of the liquid metal. We are developing a 3-dimentional, nonlinear MHD code to simulate this liquid metal disk experiment. Since experimental geometry is similar to the classical Taylor-Couette experiment of water, we follow numerical algorithms developed for Navier-Stokes simulations for Taylor-Couette instability. In our code, time development of viscous, resistive, and incompressible MHD equation is solved by the spectral method. Variables are expanded by Chebyshev polynomials in radial and vertical directions. Fourier expansion is used in the azimuthal direction. Time splitting method is used for the temporal integration. We will report latest simulation results with 3D, nonlinear effects. Special focus will be on the nonlinear stage of the instability. Effects of viscous boundary layers on the angular momentum transport will be discussed. Physical mechanism of MRI will also be presented.

  1. Gallium scanning in lymphoid interstitial pneumonitis of children with AIDS

    SciTech Connect

    Schiff, R.G.; Kabat, L.; Kamani, N.

    1987-12-01

    Lymphoid interstitial pneumonitis (LIP) is a frequent pulmonary complication in the child with the acquired immune deficiency syndrome (AIDS) and human immunodeficiency virus (HIV) infection. We report the gallium scan findings in two children with AIDS and LIP. Gallium scintigraphy in both children demonstrated increased radionuclide concentration throughout the lungs, a pattern indistinguishable scintigraphically from that of Pneumocystis carinii pneumonia (PCP). This should alert nuclear medicine practitioners and referring physicians to another cause of diffusely increased gallium uptake in the lungs of patients with AIDS.

  2. Antitumor effect of novel gallium compounds and efficacy of nanoparticle-mediated gallium delivery in lung cancer.

    PubMed

    Wehrung, Daniel; Oyewumi, Moses O

    2012-02-01

    The widespread application of gallium (Ga) in cancer therapy has been greatly hampered by lack of specificity resulting in poor tumor accumulation and retention. To address the challenge, two lipophilic gallium (III) compounds (gallium hexanedione; GaH and gallium acetylacetonate; GaAcAc) were synthesized and antitumor studies were conducted in human lung adenocarcinoma (A549) cells. Nanoparticles (NPs) containing various concentrations of the Ga compounds were prepared using a binary mixture of Gelucire 44/14 and cetyl alcohol as matrix materials. NPs were characterized based on size, morphology, stability and biocompatibility. Antitumor effects of free or NP-loaded Ga compounds were investigated based on cell viability, production of reactive oxygen species and reduction of mitochondrial potential. Compared to free Ga compounds, cytotoxicity of NP-loaded Ga (5-150 microg/ml) was less dependent on concentration and incubation time (exposure) with A549 cells. NP-mediated delivery (5-150 microg Ga/ml) enhanced antitumor effects of Ga compounds and the effect was pronounced at: (i) shorter incubation times; and (ii) at low concentrations of gallium (approximately 50 microg/ml) (p < 0.0006). Additional studies showed that NP-mediated Ga delivery was not dependent on transferrin receptor uptake mechanism (p > 0.13) suggesting the potential in overcoming gallium resistance in some tumors. In general, preparation of stable and biocompatible NPs that facilitated Ga tumor uptake and antitumor effects could be effective in gallium-based cancer therapy. PMID:22515104

  3. Fabrication, performance and degradation mechanism of aluminum gallium nitride/gallium nitride heterostructure field-effect transistors

    NASA Astrophysics Data System (ADS)

    Kim, Hyungtak

    Gallium nitride (GaN) has attracted a lot of attention as the next generation of semiconductor material for microwave power application. The unique and superior material properties of GaN and its heterostructure, such as excellent transport property, high breakdown voltage and sheet carrier concentration, and thermal and mechanical stabilities, enable AlGaN/GaN heterostructure field effect transistors (HFETs) to deliver unprecedented levels of microwave power performance. Potential applications include ultra-wide bandwidth communications and radar systems, wireless base stations, and communications satellites. Tremendous efforts to realize the potential of Al-GaN/GaN HFETs have been made over the last decade focusing on improving microwave power performance via optimizing material growth and semiconductor processing technologies. As the device performance is getting mature, the device's reliability becomes a major concern for manufacturability of commercially available AlGaN/GaN HFETs. However, comprehensive study on the reliability of these devices is still lacking. This dissertation describes the fabrication, performance and degradation characteristics and mechanism of AlGaN/GaN HFETs. The devices were fabricated with alloyed Ti/Al/Ti/Au ohmic contact and Ni/Au mushroom gate contact using E-beam lithography. The device's microwave performance was significantly improved after SiN passivation due to reduced surface effects. Several degradation modes, primarily a decrease of the output current and microwave output power density, were observed under various electrical stress tests including high current stress, high field stress, and RF overdrive. To further investigate the physical mechanism of observed degradations, SiN passivation, pulsed IV (gate lag), low frequency noise measurements, deep level transient spectroscopy (DLTS), and scanning kelvin probe microscopy (SKPM) have all been employed with hot electron stress testing. The results clearly demonstrated that charge accumulation and trap creation at the semiconductor surface and interface induced by hot electron effects are responsible for observed degradation.

  4. Measurement of arsenic and gallium content of gallium arsenide semiconductor waste streams by ICP-MS.

    PubMed

    Torrance, Keith W; Keenan, Helen E; Hursthouse, Andrew S; Stirling, David

    2010-01-01

    The chemistry of semiconductor wafer processing liquid waste, contaminated by heavy metals, was investigated to determine arsenic content. Arsenic and gallium concentrations were determined for waste slurries collected from gallium arsenide (GaAs) wafer processing at three industrial sources and compared to slurries prepared under laboratory conditions. The arsenic and gallium content of waste slurries was analyzed using inductively coupled plasma mass-spectrometry (ICP-MS) and it is reported that the arsenic content of the waste streams was related to the wafer thinning process, with slurries from wafer polishing having the highest dissolved arsenic content at over 1,900 mgL(-1). Lapping slurries had much lower dissolved arsenic (< 90 mgL(-1)) content, but higher particulate contents. It is demonstrated that significant percentage of GaAs becomes soluble during wafer lapping. Grinding slurries had the lowest dissolved arsenic content at 15 mgL(-1). All three waste streams are classified as hazardous waste, based on their solids content and dissolved arsenic levels and treatment is required before discharge or disposal. It is calculated that as much as 93% of material is discarded through the entire GaAs device manufacturing process, with limited recycling. Although gallium can be economically recovered from waste slurries, there is little incentive to recover arsenic, which is mostly landfilled. Options for treating GaAs processing waste streams are reviewed and some recommendations made for handling the waste. Therefore, although the quantities of hazardous waste generated are miniscule in comparison to other industries, sustainable manufacturing practices are needed to minimize the environmental impact of GaAs semiconductor device fabrication. PMID:20390892

  5. The dimeric nature of bonding in gallium: from small clusters to the α-gallium phase.

    PubMed

    Tonner, Ralf; Gaston, Nicola

    2014-11-28

    We consider the structural similarity of small gallium clusters to the bulk structure of α-gallium, which has been previously described as a molecular metal, via density functional theory-based computations. Previous calculations have shown that the tetramer, the hexamer, and the octamer of gallium are all structurally similar to the α-phase. We perform an analysis of the bonding in these clusters in terms of the molecular orbitals and atoms in molecules description in order to assess whether we can see similarities at these sizes to the bonding pattern, which is ascribed to the co-existence of covalent and metallic bonding in the bulk. The singlet Ga4 and Ga8 clusters can be constructed in a singlet ground state from the Ga-dimers in the first excited triplet state of the Ga2-molecule, the (3)Σg(-) state. Molecular orbital (MO) analysis confirms that the dimer is an essential building block of these small clusters. Comparison of the AIM characteristics of the bonds within the clusters to the bonds in the bulk α-phase supports the identification of the covalent bond in the bulk as related to the (3)Σg(-) state of the dimer. PMID:25294298

  6. Usefulness of gallium-67 citrate scanning in testicular seminoma

    SciTech Connect

    Willan, B.D.; Penney, H.; Castor, W.R.; McGowan, D.G.

    1987-10-01

    An analysis of 77 consecutive patients with a histologic diagnosis of seminoma testis, assessed and treated at the Cross Cancer Institute between 1977 and 1982, is presented. Ga-67 citrate was first used in the assessment of patients with malignant testicular tumors in 1973. Following three years of study that supported the observation of the gallium-avid nature of seminoma, gallium scans became routine in the initial staging assessment and were used also when recurrence was suspected. From 1977 through 1982, 72 patients with biopsy-proven seminoma testis were assessed initially for extent of disease by Ga-67 scanning. Comparison with intravenous pyelography and bipedal lymphography was possible for accuracy of tumor assessment. The scan sensitivity was 83%, and the specificity was 95%. During the same period, gallium was studied in nonseminomatous testicular tumors but the results were disappointing and its use was discontinued. The gallium-avid nature of seminoma testis may be useful in determining the extent of disease.

  7. Ellipsometric study of silicon nitride on gallium arsenide

    NASA Technical Reports Server (NTRS)

    Alterovitz, S. A.; Bu-Abbud, G. H.; Woollam, J. A.; Liu, D.; Chung, Y.; Langer, D.

    1982-01-01

    A method for optimizing the sensitivity of ellipsometric measurements for thin dielectric films on semiconductors is described in simple physical terms. The technique is demonstrated for the case of sputtered silicon nitride films on gallium arsenide.

  8. Gallium-67 uptake in the lung associated with metastatic calcification

    SciTech Connect

    Auerbach, J.M.; Ho, J.

    1981-03-01

    The case of a patient in whom pulmonary calcification appeared rapidly, accompanied by diffuse gallium-67 uptake in the lungs is reported. This finding, associated with metastatic calcification in the absence of inflammation or neoplasm, has not been previously reported.

  9. Preliminary Experimental Measurements for a Gallium Electromagnetic (GEM) Thruster

    NASA Technical Reports Server (NTRS)

    Thomas, Robert E.; Burton, Rodney L.; Glumac, Nick G.; Polzin, Kurt A.

    2007-01-01

    A low-energy gallium plasma source is used to perform a spatially and temporally broad spectroscopic survey in the 220-520 nm range. Neutral, singly, and doubly ionized gallium are present in a 20 J, 1.8 kA (peak) arc discharge operating with a central cathode. When the polarity of the inner electrode is reversed the discharge current and arc voltage waveforms remain similar. Utilizing a central anode configuration, multiple Ga lines are absent in the 270-340 nm range. In addition, neutral and singly ionized Fe spectral lines are present, indicating erosion of the outer electrode. With graphite present on the insulator to facilitate breakdown, line emission from the gallium species is further reduced and while emissions from singly and doubly ionized carbon atoms and molecular carbon (C2) radicals are observed. These data indicate that a significant fraction of energy is shifted from the gallium and deposited into the various carbon species.

  10. Computer simulation of radiation damage in gallium arsenide

    NASA Technical Reports Server (NTRS)

    Stith, John J.; Davenport, James C.; Copeland, Randolph L.

    1989-01-01

    A version of the binary-collision simulation code MARLOWE was used to study the spatial characteristics of radiation damage in proton and electron irradiated gallium arsenide. Comparisons made with the experimental results proved to be encouraging.

  11. Magnetic properties of epoxy-bonded iron-gallium particulate composites

    NASA Astrophysics Data System (ADS)

    Walters, K.; Busbridge, S.; Walters, S.

    2013-02-01

    This paper presents the production process and the results of investigations into the microstructure and magnetic properties of epoxy-bonded iron-gallium (Galfenol) particulate composites. The manufactured composites consist of powdered Fe80Ga20 alloy particles of three different size distributions (ranging from 20 to 200 ?m), bonded in an epoxy matrix with a filling factor of 0.80. The filling factor is defined as the ratio of the volume of Fe-Ga powder to the total volume of the composites constituents. The microstructure of the powdered alloy has been examined using x-ray diffractometry (XRD), and Mssbauer spectroscopy. Results for the measured magnetic hysteresis loop (B-H curve), static magnetostriction (?) versus applied field and dynamic relative permeability (?r33) are presented for the alloy in the forms of bulk material, powders and composites subsequently manufactured. The highest value of magnetostriction (360 ppm) has been found in the composite with grain size in the range of 50-100 ?m. On reversing the magnetic field direction, large magnetostrictive hysteresis for these samples has been observed. The value of ?r33 at a given applied magnetic bias field has been found to decrease with decreasing particle size.

  12. Direct Band Gap Wurtzite Gallium Phosphide Nanowires

    PubMed Central

    2013-01-01

    The main challenge for light-emitting diodes is to increase the efficiency in the green part of the spectrum. Gallium phosphide (GaP) with the normal cubic crystal structure has an indirect band gap, which severely limits the green emission efficiency. Band structure calculations have predicted a direct band gap for wurtzite GaP. Here, we report the fabrication of GaP nanowires with pure hexagonal crystal structure and demonstrate the direct nature of the band gap. We observe strong photoluminescence at a wavelength of 594 nm with short lifetime, typical for a direct band gap. Furthermore, by incorporation of aluminum or arsenic in the GaP nanowires, the emitted wavelength is tuned across an important range of the visible light spectrum (555–690 nm). This approach of crystal structure engineering enables new pathways to tailor materials properties enhancing the functionality. PMID:23464761

  13. Optical properties of gadolinium gallium garnet.

    PubMed

    Wood, D L; Nassau, K

    1990-09-01

    The refractive index, the temperature coefficient of the refractive index, and the optical transparency of gadolinium gallium garnet are reported as a function of wavelength from the near UV to the middle IR. The materialis transparent enough for good optical components between 0.36 and 6.0 microm, and the refractive index ranges from 2.0 at the UV end to 1.8 at the IR end of the spectrum. The wavelength dependence of index is expressed as a three-term Sellmeier formula with agreement better than two parts in the fourth decimal between calculated and experimental values. Variations in composition depending on growth from various melts (e.g., stoichiometric vs congruent) have no effect on the optical parameters at this level of precision. PMID:20567472

  14. Gallium arsenide solar array subsystem study

    NASA Technical Reports Server (NTRS)

    Miller, F. Q.

    1982-01-01

    The effects on life cycle costs of a number of technology areas are examined for a gallium arsenide space solar array. Four specific configurations were addressed: (1) a 250 KWe LEO mission - planer array; (2) a 250 KWe LEO mission - with concentration; (3) a 50 KWe GEO mission planer array; (4) a 50 KWe GEO mission - with concentration. For each configuration, a baseline system conceptual design was developed and the life cycle costs estimated in detail. The baseline system requirements and design technologies were then varied and their relationships to life cycle costs quantified. For example, the thermal characteristics of the baseline design are determined by the array materials and masses. The thermal characteristics in turn determine configuration, performance, and hence life cycle costs.

  15. Gallium Arsenide solar cell radiation damage experiment

    NASA Technical Reports Server (NTRS)

    Maurer, R. H.; Kinnison, J. D.; Herbert, G. A.; Meulenberg, A.

    1991-01-01

    Gallium arsenide (GaAs) solar cells for space applications from three different manufactures were irradiated with 10 MeV protons or 1 MeV electrons. The electrical performance of the cells was measured at several fluence levels and compared. Silicon cells were included for reference and comparison. All the GaAs cell types performed similarly throughout the testing and showed a 36 to 56 percent power areal density advantage over the silicon cells. Thinner (8-mil versus 12-mil) GaAs cells provide a significant weight reduction. The use of germanium (Ge) substrates to improve mechanical integrity can be implemented with little impact on end of life performance in a radiation environment.

  16. Radiation damage of gallium arsenide production cells

    NASA Technical Reports Server (NTRS)

    Mardesich, N.; Garlick, G. F. J.

    1987-01-01

    High-efficiency gallium arsenide cells, made by the liquid epitaxy method (LPE), have been irradiated with 1-MeV electrons up to fluences of 10 to the 16th e/sq cm. Measurements have been made of cell spectral response and dark and light-excited current-voltage characteristics and analyzed using computer-based models to determine underlying parameters such as damage coefficients. It is possible to use spectral response to sort out damage effects in the different cell component layers. Damage coefficients are similar to other reported in the literature for the emitter and buffer (base). However, there is also a damage effect in the window layer and possibly at the window emitter interface similar to that found for proton-irradiated liquid-phase epitaxy-grown cells. Depletion layer recombination is found to be less than theoretically expected at high fluence.

  17. Cavity optomechanics in gallium phosphide microdisks

    SciTech Connect

    Mitchell, Matthew; Barclay, Paul E.; Hryciw, Aaron C.

    2014-04-07

    We demonstrate gallium phosphide (GaP) microdisk optical cavities with intrinsic quality factors >2.8 × 10{sup 5} and mode volumes <10(λ/n){sup 3}, and study their nonlinear and optomechanical properties. For optical intensities up to 8.0 × 10{sup 4} intracavity photons, we observe optical loss in the microcavity to decrease with increasing intensity, indicating that saturable absorption sites are present in the GaP material, and that two-photon absorption is not significant. We observe optomechanical coupling between optical modes of the microdisk around 1.5 μm and several mechanical resonances, and measure an optical spring effect consistent with a theoretically predicted optomechanical coupling rate g{sub 0}/2π∼30 kHz for the fundamental mechanical radial breathing mode at 488 MHz.

  18. The Soviet-American Gallium Experiment (SAGE)

    SciTech Connect

    Garvey, G.T.

    1989-01-01

    It is a great pleasure for me to have been asked by Louis Rosen to tell you about the Soviet-American Gallium Experiment (SAGE). This undertaking is a multi-institutional collaboration among scientists from the Institute for Nuclear Research, Moscow (INR), Los Alamos National Laboratory (LANL), and several US universities. Its purpose is to measure the number of low-energy electron neutrinos emitted from the Sun that arrive at this planet. As such, it is an extremely important experiment, touching on fundamental physics issues as well as solar dynamics. In contrast to the strategic overviews, plans, and hopes for international collaboration presented earlier today, SAGE is an ongoing working effort with high hopes of producing the first measurement of the Sun's low-energy neutrino flux. This paper reviews this experiment. 3 refs., 3 figs.

  19. The effect of copper and gallium compounds on ribonucleotide reductase

    SciTech Connect

    Narasimhan, J.

    1992-01-01

    The mode of action of copper complexes (CuL and CuKTS) and gallium compounds (gallium nitrate and citrate) in cytotoxicity was studied. The effects of these agents on the enzyme ribonucleotide reductase was investigated by monitoring the tyrosyl free radical present in the active site of the enzyme through electron spin resonance (ESR) spectroscopy. Ribonucleotide reductase, a key enzyme in cellular proliferation, consists of two subunits. M1, a dimer of molecular weight 170,000 contains the substrate and effector binding sites. M2, a dimer of molecular weight 88,000, contains non-heme iron and tyrosyl free radical essential for the activity of the enzyme. In studies using copper complexes, the cellular oxidative chemistry was examined by ESR studies on adduct formation with membranes, and oxidation of thiols. Membrane thiols were oxidized through the reduction of the ESR signal of the thiol adduct and the analysis of sulfhydryl content. Using the radiolabel [sup 59]Fe, the inhibitory action of copper thiosemicarbazones on cellular iron uptake was shown. The inhibitory action of CuL on ribonucleotide reductase was shown by the quenching of the tyrosyl free radical on the M2 subunit. The hypothesis that gallium directly interacts with the M2 subunit of the enzyme and displaces the iron from it was proven. The tyrosyl free radical signal from cell lysates was inhibited by the direct addition of gallium compounds. Gallium content in the cells was measured by a fluorimetric method, to ensure the presence of sufficient amounts of gallium to compete with the iron in the M2 subunit. The enzyme activity, measured by the conversion of [sup 14]C-CDP to the labeled deoxy CDP, was inhibited by the addition of gallium nitrate in a cell free assay system. The immunoprecipitation studies of the [sup 59]Fe labeled M2 protein using the monoclonal antibody directed against this subunit suggested that gallium releases iron from the M2 subunit.

  20. Ultrasonic solvent extraction of gallium with Kelex 100

    NASA Astrophysics Data System (ADS)

    Pesic, Batric; Zhou, Taili

    1989-06-01

    Using ultrasound for the solvent extraction of gallium with Kelex 100 dramatically increased the rates (up to 15 times) of extraction in both artificial and real solutions. Among the modifiers, 2-undecanone performed the best; among the diluents, Escaid 200 produced the best results. With the application of ultrasound, temperature did not effect gallium extraction. Further, through the intermittent use of ultrasound, energy consumption can be decreased significantly.

  1. Complexometric determination of gallium with calcein blue as indicator

    USGS Publications Warehouse

    Elsheimer, H.N.

    1967-01-01

    A metalfluorechromic indicator, Calcein Blue, has been used for the back-titration of milligram amounts of EDTA in presence of gallium complexes. The indicator was used in conjunction with an ultraviolet titration assembly equipped with a cadmium sulphide detector cell and a microammeter for enhanced end-point detection. The result is a convenient and rapid method with an accuracy approaching 0.1 % and a relative standard deviation of about 0.4% for 10 mg of gallium. ?? 1967.

  2. Generator for ionic gallium-68 based on column chromatography

    DOEpatents

    Neirinckx, Rudi D.; Davis, Michael A.

    1981-01-01

    A physiologically acceptable solution of gallium-68 fluorides, having an activity of 0.1 to 50 millicuries per milliliter of solution is provided. The solution is obtained from a generator comprising germanium-68 hexafluoride bound to a column of an anion exchange resin which forms gallium-68 in situ by eluting the column with an acid solution to form a solution containing .sup.68 Ga-fluorides. The solution then is neutralized prior to administration.

  3. Light Induced Soliton Switching at the Gallium-Silica Interface

    NASA Astrophysics Data System (ADS)

    Naruka, Preeti; Bissa, Shivangi

    In the present paper, we have investigated the solitonic characteristics of a pulse passing through an interface separating two nonlinear media. The first media is a thin film of gallium nanoparticles which show switching properties under optical excitation and second is a monomode optical fiber. Soliton propagation in three different phases of gallium nanoparticles have been analyzed by using the method of phase-plane analysis. Also, the critical power required for soliton propagation has been calculated.

  4. Inhalation developmental toxicology studies: Gallium arsenide in mice and rats

    SciTech Connect

    Mast, T.J.; Greenspan, B.J.; Dill, J.A.; Stoney, K.H.; Evanoff, J.J.; Rommereim, R.L.

    1990-12-01

    Gallium arsenide is a crystalline compound used extensively in the semiconductor industry. Workers preparing solar cells and gallium arsenide ingots and wafers are potentially at risk from the inhalation of gallium arsenide dust. The potential for gallium arsenide to cause developmental toxicity was assessed in Sprague- Dawley rats and CD-1 (Swiss) mice exposed to 0, 10, 37, or 75 mg/m{sup 3} gallium arsenide, 6 h/day, 7 days/week. Each of the four treatment groups consisted of 10 virgin females (for comparison), and {approx}30 positively mated rats or {approx}24 positively mated mice. Mice were exposed on 4--17 days of gestation (dg), and rats on 4--19 dg. The day of plug or sperm detection was designated as 0 dg. Body weights were obtained throughout the study period, and uterine and fetal body weights were obtained at sacrifice (rats, 20 dg; mice, 18 dg). Implants were enumerated and their status recorded. Live fetuses were sexed and examined for gross, visceral, skeletal, and soft-tissue craniofacial defects. Gallium and arsenic concentrations were determined in the maternal blood and uterine contents of the rats (3/group) at 7, 14, and 20 dg. 37 refs., 11 figs., 30 tabs.

  5. Method of fabricating germanium and gallium arsenide devices

    NASA Technical Reports Server (NTRS)

    Jhabvala, Murzban (Inventor)

    1990-01-01

    A method of semiconductor diode fabrication is disclosed which relies on the epitaxial growth of a precisely doped thickness layer of gallium arsenide or germanium on a semi-insulating or intrinsic substrate, respectively, of gallium arsenide or germanium by either molecular beam epitaxy (MBE) or by metal-organic chemical vapor deposition (MOCVD). The method involves: depositing a layer of doped or undoped silicon dioxide on a germanium or gallium arsenide wafer or substrate, selectively removing the silicon dioxide layer to define one or more surface regions for a device to be fabricated thereon, growing a matched epitaxial layer of doped germanium or gallium arsenide of an appropriate thickness using MBE or MOCVD techniques on both the silicon dioxide layer and the defined one or more regions; and etching the silicon dioxide and the epitaxial material on top of the silicon dioxide to leave a matched epitaxial layer of germanium or gallium arsenide on the germanium or gallium arsenide substrate, respectively, and upon which a field effect device can thereafter be formed.

  6. Data in support of Gallium (Ga3+) antibacterial activities to counteract E. coli and S. epidermidis biofilm formation onto pro-osteointegrative titanium surfaces

    PubMed Central

    Cochis, A.; Azzimonti, B.; Sorrentino, R.; Della Valle, C.; De Giglio, E.; Bloise, N.; Visai, L.; Bruni, G.; Cometa, S.; Pezzoli, D.; Candiani, G.; Rimondini, L.; Chiesa, R.

    2016-01-01

    This paper contains original data supporting the antibacterial activities of Gallium (Ga3+)-doped pro-osteointegrative titanium alloys, obtained via Anodic Spark Deposition (ASD), as described in “The effect of silver or gallium doped titanium against the multidrug resistant Acinetobacter baumannii” (Cochis et al. 2016) [1]. In this article we included an indirect cytocompatibility evaluation towards Saos2 human osteoblasts and extended the microbial evaluation of the Ga3+ enriched titanium surfaces against the biofilm former Escherichia coli and Staphylococcus epidermidis strains. Cell viability was assayed by the Alamar Blue test, while bacterial viability was evaluated by the metabolic colorimetric 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assay. Finally biofilm morphology was analyzed by Scanning Electron Microscopy (SEM). Data regarding Ga3+ activity were compared to Silver. PMID:26909385

  7. Data in support of Gallium (Ga(3+)) antibacterial activities to counteract E. coli and S. epidermidis biofilm formation onto pro-osteointegrative titanium surfaces.

    PubMed

    Cochis, A; Azzimonti, B; Sorrentino, R; Della Valle, C; De Giglio, E; Bloise, N; Visai, L; Bruni, G; Cometa, S; Pezzoli, D; Candiani, G; Rimondini, L; Chiesa, R

    2016-03-01

    This paper contains original data supporting the antibacterial activities of Gallium (Ga(3+))-doped pro-osteointegrative titanium alloys, obtained via Anodic Spark Deposition (ASD), as described in "The effect of silver or gallium doped titanium against the multidrug resistant Acinetobacter baumannii" (Cochis et al. 2016) [1]. In this article we included an indirect cytocompatibility evaluation towards Saos2 human osteoblasts and extended the microbial evaluation of the Ga(3+) enriched titanium surfaces against the biofilm former Escherichia coli and Staphylococcus epidermidis strains. Cell viability was assayed by the Alamar Blue test, while bacterial viability was evaluated by the metabolic colorimetric 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assay. Finally biofilm morphology was analyzed by Scanning Electron Microscopy (SEM). Data regarding Ga(3+) activity were compared to Silver. PMID:26909385

  8. Application of ultrasound in solvent extraction of nickel and gallium

    SciTech Connect

    Pesic, B.

    1996-07-01

    The effects of ultrasound on the rate of solvent extraction of nickel with Lix 65N and Lix 70, and gallium with Kelex 100 were investigated. These solvent extraction systems are noted by their sluggish nature. Low frequency (20 kHz) ultrasound increased the rates of extraction of nickel by factors of four to seven. The ultrasound had no effect on the final chemical equilibrium. Gallium extraction rates were enhanced with the use of ultrasound by as much as a factor of 15. Again, the ultrasound had no effect on extraction equilibrium. For both nickel and gallium, the enhanced rates were attributed to increased interfacial surface area associated with ultrasonically induced cavitation and microdroplet formation. The stability of the microdroplets permitted intermittent application of ultrasound with corresponding decreases in ultrasonic energy requirements. The lowest energy consumption was observed with short (0.25 to 5 s) bursts of high power (41 to 61 W) ultrasonic inputs. The study also provided insight into the factors that affect the complex extraction of gallium from sodium aluminate solutions. The rate controlling step was found to be the dehydration of the gallate ion, Ga(OH)4, and the first complex formation between gallium and Kelex 100. Sodium was found to enhance the extraction rate up to a point, beyond which increased concentration was detrimental. Increasing aluminum concentration was found to slow extraction rates. Modifiers and diluents were shown to markedly affect extraction rates even without ultrasound. Ketone modifiers, particularly 2-undecanone, when used with Kermac 470B or Escaid 200 diluents enhanced extraction rates of gallium to the point that the use of ultrasound provided no additional benefits. The positive effects of ketone modifiers for the solvent extraction of gallium had not been previously reported.

  9. Gallium based low-interaction anions

    DOEpatents

    King, Wayne A.; Kubas, Gregory J.

    2000-01-01

    The present invention provides: a composition of the formula M.sup.+x (Ga(Y).sub.4.sup.-).sub.x where M is a metal selected from the group consisting of lithium, sodium, potassium, cesium, calcium, strontium, thallium, and silver, x is an integer selected from the group consisting of 1 or 2, each Y is a ligand selected from the group consisting of aryl, alkyl, hydride and halide with the proviso that at least one Y is a ligand selected from the group consisting of aryl, alkyl and halide; a composition of the formula (R).sub.x Q.sup.+ Ga(Y).sub.4.sup.- where Q is selected from the group consisting of carbon, nitrogen, sulfur, phosphorus and oxygen, each R is a ligand selected from the group consisting of alkyl, aryl, and hydrogen, x is an integer selected from the group consisting of 3 and 4 depending upon Q, and each Y is a ligand selected from the group consisting of aryl, alkyl, hydride and halide with the proviso that at least one Y is a ligand selected from the group consisting of aryl, alkyl and halide; an ionic polymerization catalyst composition including an active cationic portion and a gallium based weakly coordinating anion; and bridged anion species of the formula M.sup.+x.sub.y [X(Ga(Y.sub.3).sub.z ].sup.-y.sub.x where M is a metal selected from the group consisting of lithium, sodium, potassium, magnesium, cesium, calcium, strontium, thallium, and silver, x is an integer selected from the group consisting of 1 or 2, X is a bridging group between two gallium atoms, y is an integer selected from the group consisting 1 and 2, z is an integer of at least 2, each Y is a ligand selected from the group consisting of aryl, alkyl, hydride and halide with the proviso that at least one Y is a ligand selected from the group consisting of aryl, alkyl and halide.

  10. Gallium a unique anti-resorptive agent in bone: Preclinical studies on its mechanisms of action

    SciTech Connect

    Bockman, R.; Adelman, R.; Donnelly, R.; Brody, L.; Warrell, R. ); Jones, K.W. )

    1990-01-01

    The discovery of gallium as a new and unique agent for the treatment of metabolic bone disorders was in part fortuitous. Gallium is an exciting new therapeutic agent for the treatment of pathologic states characterized by accelerated bone resorption. Compared to other therapeutic metal compounds containing platinum or germanium, gallium affects its antiresorptive action without any evidence of a cytotoxic effect on bone cells. Gallium is unique amongst all therapeutically available antiresorptive agents in that it favors bone formation. 18 refs., 1 fig.

  11. Alloy materials

    DOEpatents

    Hans Thieme, Cornelis Leo; Thompson, Elliott D.; Fritzemeier, Leslie G.; Cameron, Robert D.; Siegal, Edward J.

    2002-01-01

    An alloy that contains at least two metals and can be used as a substrate for a superconductor is disclosed. The alloy can contain an oxide former. The alloy can have a biaxial or cube texture. The substrate can be used in a multilayer superconductor, which can further include one or more buffer layers disposed between the substrate and the superconductor material. The alloys can be made a by process that involves first rolling the alloy then annealing the alloy. A relatively large volume percentage of the alloy can be formed of grains having a biaxial or cube texture.

  12. 40 CFR 421.180 - Applicability: Description of the primary and secondary germanium and gallium subcategory.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... primary and secondary germanium and gallium subcategory. 421.180 Section 421.180 Protection of Environment... POINT SOURCE CATEGORY Primary and Secondary Germanium and Gallium Subcategory § 421.180 Applicability: Description of the primary and secondary germanium and gallium subcategory. The provisions of this subpart...

  13. 40 CFR 421.180 - Applicability: Description of the primary and secondary germanium and gallium subcategory.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... primary and secondary germanium and gallium subcategory. 421.180 Section 421.180 Protection of Environment... POINT SOURCE CATEGORY Primary and Secondary Germanium and Gallium Subcategory § 421.180 Applicability: Description of the primary and secondary germanium and gallium subcategory. The provisions of this subpart...

  14. Pure silver ohmic contacts to N- and P- type gallium arsenide materials

    DOEpatents

    Hogan, Stephen J.

    1986-01-01

    Disclosed is an improved process for manufacturing gallium arsenide semiconductor devices having as its components an n-type gallium arsenide substrate layer and a p-type gallium arsenide diffused layer. The improved process comprises forming a pure silver ohmic contact to both the diffused layer and the substrate layer, wherein the n-type layer comprises a substantially low doping carrier concentration.

  15. Process for forming pure silver ohmic contacts to N- and P-type gallium arsenide materials

    DOEpatents

    Hogan, S.J.

    1983-03-13

    Disclosed is an improved process for manufacturing gallium arsenide semiconductor devices having as its components a n-type gallium arsenide substrate layer and a p-type gallium arsenide diffused layer. The improved process comprises forming a pure silver ohmic contact to both the diffuse layer and the substrate layer wherein the n-type layer comprises a substantially low doping carrier concentration.

  16. Determination of gallium in an iron-aluminium matrix by solvent extraction and flame emission spectroscopy.

    PubMed

    Cresser, M S; Torrent-Castellet, J

    1972-11-01

    Solvent extraction of gallium(III) into methyl isobutyl ketone from hydrochloric acid solutions containing titanium (III) sulphate provides a rapid method for separation of gallium from an iron/aluminium matrix and may be employed to eliminate the interference of these elements in the flame emission spectrometric determination of gallium. PMID:18961209

  17. 40 CFR 421.180 - Applicability: Description of the primary and secondary germanium and gallium subcategory.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... primary and secondary germanium and gallium subcategory. 421.180 Section 421.180 Protection of Environment... POINT SOURCE CATEGORY Primary and Secondary Germanium and Gallium Subcategory § 421.180 Applicability: Description of the primary and secondary germanium and gallium subcategory. The provisions of this subpart...

  18. 40 CFR 421.180 - Applicability: Description of the primary and secondary germanium and gallium subcategory.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... primary and secondary germanium and gallium subcategory. 421.180 Section 421.180 Protection of Environment... POINT SOURCE CATEGORY Primary and Secondary Germanium and Gallium Subcategory § 421.180 Applicability: Description of the primary and secondary germanium and gallium subcategory. The provisions of this subpart...

  19. 40 CFR 421.180 - Applicability: Description of the primary and secondary germanium and gallium subcategory.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... primary and secondary germanium and gallium subcategory. 421.180 Section 421.180 Protection of Environment... POINT SOURCE CATEGORY Primary and Secondary Germanium and Gallium Subcategory § 421.180 Applicability: Description of the primary and secondary germanium and gallium subcategory. The provisions of this subpart...

  20. Preliminary Spectroscopic Measurements for a Gallium Electromagnetic (GEM) Thruster

    NASA Technical Reports Server (NTRS)

    Thomas, Robert E.; Burton, Rodney L.; Glumac, Nick G.; Polzin, Kurt A.

    2007-01-01

    As a propellant option for electromagnetic thrusters, liquid ,gallium appears to have several advantages relative to other propellants. The merits of using gallium in an electromagnetic thruster (EMT) are discussed and estimates of discharge current levels and mass flow rates yielding efficient operation are given. The gallium atomic weight of 70 predicts high efficiency in the 1500-2000 s specific impulse range, making it ideal for higher-thrust, near-Earth missions. A spatially and temporally broad spectroscopic survey in the 220-520 nm range is used to determine which species are present in the plasma and estimate electron temperature. The spectra show that neutral, singly, and doubly ionized gallium species are present in a 20 J, 1.8 kA (peak) are discharge. With graphite present on the insulator to facilitate breakdown, singly and doubly ionized carbon atoms are also present, and emission is observed from molecular carbon (CZ) radicals. A determination of the electron temperature was attempted using relative emission line data, and while the spatially and temporally averaged, spectra don't fit well to single temperatures, the data and presence of doubly ionized gallium are consistent with distributions in the 1-3 eV range.

  1. Gallium scintigraphy in a case of septic cavernous sinus thrombosis

    SciTech Connect

    Palestro, C.J.; Malat, J.; Gladstone, A.G.; Richman, A.H.

    1986-09-01

    Septic cavernous sinus thrombosis, a relatively uncommon disease entity, frequently can be fatal. Early diagnosis is imperative in order that appropriate treatment be instituted. A 59-year-old woman who was admitted to our institution with complaints of diplopia, blurred vision and fevers that developed following a tooth extraction is presented. Initial CT and lumbar puncture on the day of admission were totally normal. A repeat CT performed 48 hours after admission, on the same day as gallium imaging, demonstrated findings consistent with cavernous sinus thrombosis. Gallium imaging demonstrated intense uptake in the left cavernous sinus and left orbit as well as moderately increased activity in the right cavernous sinus and orbit, confirming infection. The patient was treated with antibiotics, and repeat CT and gallium imaging were performed ten days later, both of which demonstrated near total resolution of the disease process. Conceivably, if gallium imaging had been initiated on the day of admission it may have been the first study to demonstrate an infectious process in the cavernous sinus. Gallium imaging should be considered as a diagnostic tool in the noninvasive workup of this entity.

  2. Synthesis and characterization of gallium colloidal nanoparticles.

    PubMed

    Meléndrez, M F; Cárdenas, G; Arbiol, J

    2010-06-15

    In this work, gallium colloidal nanoparticles (Ga-Nps) were synthesized by chemical liquid deposition (CLD). This method involved the deposition of metallic atoms with organic solvents (THF, acetone and 2-propanol) in a freezing matrix of the solvent at 77K, in order to obtain core-shell Ga-Nps which were characterized by: FT-IR, UV-Vis, TEM, SAED and electrophoretic mobility measurements. TEM images revealed a wide distribution of the apparent size of the particles and apparent average size of 5.65, 8.11 and 13.87 nm for Ga-Nps obtained with 2-propanol, THF and acetone, respectively. UV spectra showed absorption bands of metal plasmons, interesting quantum size effects and plasmon absorption bands of particles aggregated to lambda(280) and lambda(325). Electrophoretic mobility allowed to evidence that nanoparticles had a negative charge as well as to observe that the zeta potential of the colloidal dispersions decreased over time, showing a significant tendency to the aggregation of Ga-Nps. The importance of the functionalization of metal nanoparticles with high dielectric constant solvents in the stabilization of colloidal systems was also observed. FT-IR spectroscopy revealed that the interaction of Ga surface with the solvent possibly produces a (GaC) bond. Experimental details, structural and thermal stability studies were also analyzed in this work. PMID:20378122

  3. Investigation on gallium ions impacting monolayer graphene

    NASA Astrophysics Data System (ADS)

    Wu, Xin; Zhao, Haiyan; Yan, Dong; Pei, Jiayun

    2015-06-01

    In this paper, the physical phenomena of gallium (Ga+) ion impacting monolayer graphene in the nanosculpting process are investigated experimentally, and the mechanisms are explained by using Monte Carlo (MC) and molecular dynamics (MD) simulations. Firstly, the MC method is employed to clarify the phenomena happened to the monolayer graphene target under Ga+ ion irradiation. It is found that substrate has strong influence on the damage mode of graphene. The mean sputtering yield of graphene under 30 keV Ga+ ion irradiation is 1.77 and the least ion dose to completely remove carbon atoms in graphene is 21.6 ion/nm2. Afterwards, the focused ion beam over 21.6 ion/nm2 is used for the irradiation on a monolayer graphene supported by SiO2 experimentally, resulting in the nanostructures, i.e., nanodot and nanowire array on the graphene. The performances of the nanostructures are characterized by atomic force microscopy and Raman spectrum. A plasma plume shielding model is put forward to explain the nanosculpting results of graphene under different irradiation parameters. In addition, two damage mechanisms are found existing in the fabrication process of the nanostructures by using empirical MD simulations. The results can help us open the possibilities for better control of nanocarbon devices.

  4. Gallium nitride micromechanical resonators for IR detection

    NASA Astrophysics Data System (ADS)

    Rais-Zadeh, Mina

    2012-06-01

    This paper reports on a novel technology for low-noise un-cooled detection of infrared (IR) radiation using a combination of piezoelectric, pyroelectric, electrostrictive, and resonant effects. The architecture consists of a parallel array of high-Q gallium nitride (GaN) micro-mechanical resonators coated with an IR absorbing nanocomposite. The nanocomposite absorber converts the IR energy into heat with high efficiency. The generated heat causes a shift in frequency characteristics of the GaN resonators because of pyroelectric effect. IR detection is achieved by sensing the shift in the resonance frequency and amplitude of the exposed GaN resonator as compared to a reference resonator that is included in the array. This architecture offers improved signal to noise ratio compared with conventional pyroelectric detectors as the resonant effect reduces the background noise and improves sensitivity, enabling IR detection with NEDTs below 5 mK at room temperature. GaN is chosen as the resonant material as it possesses high pyroelectric, electrostrictive, and piezoelectric coefficients and can be grown on silicon substrates for low-cost batch fabrication. Measured results of a GaN IR detector prototype and a thin-film nanocomposite IR absorber are presented in this paper.

  5. Simple method for cleaning gallium nitride (0001)

    NASA Astrophysics Data System (ADS)

    Machuca, Francisco; Liu, Zhi; Sun, Yun; Pianetta, P.; Spicer, W. E.; Pease, R. F. W.

    2002-09-01

    Achieving clean surfaces is a major and challenging requirement for the study of surfaces and surface reactions. We describe the use of synchrotron radiation (SR) to probe the electronic structure of the gallium nitride (GaN) (0001) surface that has undergone wet chemical cleaning sequences followed by heating. By using SR in the range of 200-1000 eV the core levels of Ga, N, O, and C are monitored. Immersion in a 4:1 solution of sulfuric acid (51%) to hydrogen peroxide (30%) followed by a 700 degC (200 degC below decomposition temperature) vacuum anneal (less-than-or-equal10-10 Torr) results in a reduction of carbon and oxygen coverage to a few percent of a monolayer. This suggests a weakly bound oxide of carbon being chemisorbed to the GaN surface after the sulfuric acid/hydrogen peroxide treatment and it is removed by the heating. copyright 2002 American Vacuum Society.

  6. Gallium Nitride Based Logpile Photonic Crystal

    SciTech Connect

    Subramania, Ganapathi; Li, Qiming; Lee, Yun-Ju; Figiel, Jeffrey J.; Wang, George T.; Fischer, Arthur J.

    2011-11-09

    A nine-layer logpile three-dimensional photonic crystal (3DPC) is demonstrated composed of single crystalline gallium nitride (GaN) nanorods, ~ 100 nm in size with lattice constants of 260, 280, and 300 nm with photonic band gap in the visible region. This unique GaN structure is created through a combined approach of a layer-by-layer template fabrication technique and selective metal organic chemical vapor deposition (MOCVD). These GaN 3DPC exhibit a stacking direction band gap characterized by strong optical reflectance between 380 and 500 nm. By introducing a ''line-defect'' cavity in the fifth (middle) layer of the 3DPC, a localized transmission mode with a quality factor of 25–30 is also observed within the photonic band gap. The realization of a group III nitride 3DPC with uniform features and a band gap at wavelengths in the visible region is an important step toward realizing complete control of the electromagnetic environment for group III nitride-based optoelectronic devices.

  7. Gallium nitride based logpile photonic crystals.

    PubMed

    Subramania, Ganapathi; Li, Qiming; Lee, Yun-Ju; Figiel, Jeffrey J; Wang, George T; Fischer, Arthur J

    2011-11-01

    We demonstrate a nine-layer logpile three-dimensional photonic crystal (3DPC) composed of single crystalline gallium nitride (GaN) nanorods, ∼100 nm in size with lattice constants of 260, 280, and 300 nm with photonic band gap in the visible region. This unique GaN structure is created through a combined approach of a layer-by-layer template fabrication technique and selective metal organic chemical vapor deposition (MOCVD). These GaN 3DPC exhibit a stacking direction band gap characterized by strong optical reflectance between 380 and 500 nm. By introducing a "line-defect" cavity in the fifth (middle) layer of the 3DPC, a localized transmission mode with a quality factor of 25-30 is also observed within the photonic band gap. The realization of a group III nitride 3DPC with uniform features and a band gap at wavelengths in the visible region is an important step toward realizing complete control of the electromagnetic environment for group III nitride based optoelectronic devices. PMID:21970551

  8. Energy deposition in gallium arsenide. Final report

    SciTech Connect

    McNulty, P.J.

    1985-11-12

    This report pertains to the single-event-upset phenomena in microelectronic circuits with emphasis on those resulting from nuclear reactions induced by energetic protons. The goal is to understand the detailed physical mechanisms leading to SEUs sufficiently to put calculating SEUs on a sound quantitative basis. The author previously had considerable success in predicting the charge generation in well defined slabs of silicon. The purpose of this contract was to try extending the model and the associated simulation codes to GaAs and to begin the experimental measurements necessary to test them. The Clarkson Nuclear Reaction models were modified to handle proton-induced nuclear reactions in gallium arsenide. The codes were immediately useful in analyzing the significance that the edge-effect phenomena, discovered in microbeam studies of GaAs gates, would play in increasing the SEU rates for GaAs memories. Techniques were developed using these codes for calculating SEU rates for select circuits flown in space. Two of these circuits, the 2901B and the 93L422, are responsible for SEU problems aboard US satellites. Charge-collection Measurements were carried out using the GaAs Fat-FET test structures from the Rockwell memories.

  9. Hydrogen in Gallium Nitride Grown by MOCVD

    NASA Astrophysics Data System (ADS)

    Ambacher, O.; Angerer, H.; Dimitrov, R.; Rieger, W.; Stutzmann, M.; Dollinger, G.; Bergmaier, A.

    1997-01-01

    The role of hydrogen in gallium nitride was studied on thin films of GaN on sapphire prepared at substrate temperatures in the range of 600 to 1100 °C. By using triethylgallium and ammonia as precursor and hydrogen and/or nitrogen as transport gases, we have observed a strong influence of molecular hydrogen on the deposition rate and the structural properties of epitaxial GaN. By elastic recoil detection analysis and thermal desorption measurements we were able to determine the total concentration of nitrogen, hydrogen and carbon in the bulk material. Isotope substitution of hydrogen by deuterium in the H2 carrier gas did not give rise to a noticeable deuterium incorporation, showing that the sources for hydrogen are the metalorganic precursor, ammonia or reaction products of both. Once incorporated, thermally activated hydrogen effusion from n-type GaN occurs with an activation energy of more than 3.9 eV. With the help of mass spectrometry we established hydrogen effusion from heavily magnesium-doped (2 at%) GaN at temperatures between 600 and 700 °C, which is the temperature range used for acceptor activation.

  10. Electronic Structure Calculations for Gallium Sulfide

    NASA Astrophysics Data System (ADS)

    Boyer, L. L.; Kaxiras, Efthimios

    1996-03-01

    Gallium sulfide (GaS) is reported to form an insulating phase when formed by metal-organic chemical vapor deposition on GaAs.( A.N. MacInnes, M.B. Power and A.R. Barron, Chem. of Materials 5, 1344 (1993)) Electron diffraction results and the molecular structure used for deposition suggest that the crystal structure could be a distortion of the B1 lattice structure that involves displacement of the sulfur atoms only. We have carried out local-density functional calculations using a plane wave, pseudopotential formulation to study zone boundary distortions of this lattice, consistent with experimental results. Keeping the volume fixed at the experimental value, we find that the undistorted lattice is metallic and the most promising distortion consists of a linear combination of L1+ modes, leading to a structure of Fd3m symmetry with 16 atoms per unit cell; this distortion lowers the energy substantially and produces a small band gap. However, the gap is too small and the structure is unstable with respect to volume relaxations. Calculations for distortions of the zinc-blende structure are in progress.

  11. Gallium plasmonics: deep subwavelength spectroscopic imaging of single and interacting gallium nanoparticles.

    PubMed

    Knight, Mark W; Coenen, Toon; Yang, Yang; Brenny, Benjamin J M; Losurdo, Maria; Brown, April S; Everitt, Henry O; Polman, Albert

    2015-02-24

    Gallium has recently been demonstrated as a phase-change plasmonic material offering UV tunability, facile synthesis, and a remarkable stability due to its thin, self-terminating native oxide. However, the dense irregular nanoparticle (NP) ensembles fabricated by molecular-beam epitaxy make optical measurements of individual particles challenging. Here we employ hyperspectral cathodoluminescence (CL) microscopy to characterize the response of single Ga NPs of various sizes within an irregular ensemble by spatially and spectrally resolving both in-plane and out-of-plane plasmonic modes. These modes, which include hybridized dipolar and higher-order terms due to phase retardation and substrate interactions, are correlated with finite difference time domain (FDTD) electrodynamics calculations that consider the Ga NP contact angle, substrate, and native Ga/Si surface oxidation. This study experimentally confirms previous theoretical predictions of plasmonic size-tunability in single Ga NPs and demonstrates that the plasmonic modes of interacting Ga nanoparticles can hybridize to produce strong hot spots in the ultraviolet. The controlled, robust UV plasmonic resonances of gallium nanoparticles are applicable to energy- and phase-specific applications such as optical memory, environmental remediation, and simultaneous fluorescence and surface-enhanced Raman spectroscopies. PMID:25629392

  12. Native gallium adatoms discovered on atomically-smooth gallium nitride surfaces at low temperature.

    PubMed

    Alam, Khan; Foley, Andrew; Smith, Arthur R

    2015-03-11

    In advanced compound semiconductor devices, such as in quantum dot and quantum well systems, detailed atomic configurations at the growth surfaces are vital in determining the structural and electronic properties. Therefore, it is important to investigate the surface reconstructions in order to make further technological advancements. Usually, conventional semiconductor surfaces (e.g., arsenides, phosphides, and antimonides) are highly reactive due to the existence of a high density of group V (anion) surface dangling bonds. However, in the case of nitrides, group III rich growth conditions in molecular beam epitaxy are usually preferred leading to group III (Ga)-rich surfaces. Here, we use low-temperature scanning tunneling microscopy to reveal a uniform distribution of native gallium adatoms with a density of 0.3%-0.5% of a monolayer on the clean, as-grown surface of nitrogen polar GaN(0001̅) having the centered 6 × 12 reconstruction. Unseen at room temperature, these Ga adatoms are strongly bound to the surface but move with an extremely low surface diffusion barrier and a high density saturation coverage in thermodynamic equilibrium with Ga droplets. Furthermore, the Ga adatoms reveal an intrinsic surface chirality and an asymmetric site occupation. These observations can have important impacts in the understanding of gallium nitride surfaces. PMID:25656811

  13. Determination of gallium originated from a gallium-based anticancer drug in human urine using ICP-MS.

    PubMed

    Filatova, Darya G; Seregina, Irina F; Foteeva, Lidia S; Pukhov, Vladimir V; Timerbaev, Andrei R; Bolshov, Mikhail A

    2011-05-01

    Urine analysis gives an insight into the excretion of the administered drug which is related to its reactivity and toxicity. In this work, the capability of inductively coupled plasma mass spectrometry (ICP-MS) to measure ultratrace metal levels was utilized for rapid assaying of gallium originating from the novel gallium anticancer drug, tris(8-quinolinolato)gallium(III) (GaQ(3)), in human urine. Sample dilution with 1% (v/v) HNO(3) as the only required pre-treatment was shown to prevent contamination of the sample introduction system and to reduce polyatomic interferences from sample components. The origin of the blank signal at masses of gallium isotopes, 71 and 69, was investigated using high-resolution ICP-MS and attributed, respectively, to the formation of (36)Ar(35)Cl(+) and (40)Ar(31)P(+) ions and, tentatively, to a triplet of doubly charged ions of Ba, La, and Ce. The accuracy and precision performance was tested by evaluating a set of parameters for analytical method validation. The developed assay has been applied for the determination of gallium in urine samples spiked with GaQ(3). The achieved recoveries (95-102%) and quantification limit of 0.2 μg L(-1) emphasize the practical applicability of the presented analytical approach to monitor renal elimination of GaQ(3) at all dose levels in clinical trials that are currently in progress. PMID:21359996

  14. Dipeptide-assisted growth of uniform gallium oxohydroxide spindles

    NASA Astrophysics Data System (ADS)

    Lee, Inho; Kwak, Jinyoung; Haam, Seungjoo; Lee, Sang-Yup

    2010-07-01

    The catalytic dipeptide His-Ser was used as an additive in mineralizing gallium ions to form GaOOH, a solid precursor of Ga 2O 3. This dipeptide was chosen to mimic the enzyme structure of silicatein, similar to the well-known catalytic triad of chymotrypsin. The dipeptide promoted formation of spindle-structured GaOOH under acidic conditions by behaving as a heterogeneous nucleation seed. In contrast, no well-defined, structured gallium species were produced in the absence of dipeptide. The catalytic function of the dipeptide was most pronounced at pH values in the range 3-5, which are lower than the pKa of imidazole in the His side chain. These results suggest that the catalytic role of dipeptide influences the gallium hydroxide conversion and growth. This study suggests that a designed peptide with active functionality can be further exploited to produce inorganic compounds with controlled nucleation and growth.

  15. A melting-point-of gallium apparatus for thermometer calibration.

    PubMed

    Sostman, H E; Manley, K A

    1978-08-01

    We have investigated the equilibrium melting point of gallium as a temperature fixed-point at which to calibrate small thermistor thermometers, such as those used to measure temperature in enzyme reaction analysis and other temperature-dependent biological assays. We have determined that the melting temperature of "6N" (99.999% pure) gallium is 29.770 +/- 0.002 degrees C, and that the constant-temperature plateau can be prolonged for several hours. We have designed a simple automated apparatus that exploits this phenomenon and that permits routine calibration verification of thermistor temperature probes throughout the laboratory day. We describe the physics of the gallium melt, and the design and use of the apparatus. PMID:679456

  16. Effect of bronchoscopy on localization of gallium-67 citrate

    SciTech Connect

    Phillips, B.A.; Cooper, K.R.; Fratkin, M.J.

    1983-03-01

    Bronchoscopy, bronchoalveolar lavage (BAL), and 67Ga lung scans are frequently performed for diagnosis or follow-up of patients with sarcoidosis, interstitial pneumonitis, lymphoma, infections, and bronchogenic carcinoma. Because many patients undergo all 3 of these procedures, it is important to determine what effects bronchoscopy and/or BAL may have on gallium imaging. Because 67Ga accumulates in neutrophils at the site of an inflammatory lesion as well as in those circulating in the vascular compartment, it seems reasonable to postulate that bronchoscopy could cause migration of labeled neutrophils into the lung, resulting in false positive gallium scans. To test this hypothesis, we studied 5 patients with varying chronologic relationships of 67Ga injection, gallium scanning, and bronchoscopy with BAL. In all patients, the repeat 67Ga lung scans remained normal or showed no change after bronchoscopy and BAL. We conclude that bronchoscopy with or without BAL does not cause increased 67Ga uptake by the lung.

  17. Interaction of a Liquid Gallium Jet with ISTTOK Edge Plasmas

    NASA Astrophysics Data System (ADS)

    Gomes, R. B.; Fernandes, H.; Silva, C.; Sarakovskis, A.; Pereira, T.; Figueiredo, J.; Carvalho, B.; Soares, A.; Duarte, P.; Varandas, C.; Lielausis, O.; Klyukin, A.; Platacis, E.; Tale, I.

    2008-04-01

    The use of liquid metals as plasma facing components in tokamaks has recently experienced a renewed interest stimulated by their advantages in the development of a fusion reactor. Liquid metals have been proposed to solve problems related to the erosion and neutronic activation of solid walls submitted to high power loads allowing an efficient heat exhaust from fusion devices. Presently the most promising candidate materials are lithium and gallium. However, lithium has a short liquid state range when compared, for example, with gallium that has essentially better thermal properties and lower vapor pressure. To explore further these properties, ISTTOK tokamak is being used to test the interaction of a free flying, fully formed liquid gallium jet with the plasma. The interacting, 2.3 mm diameter, jet is generated by hydrostatic pressure and has a 2.5 m/s flow velocity. The liquid metal injector has been build to allow the positioning of the jet inside the tokamak chamber, within a 13 mm range. This paper presents the first obtained experimental results concerning the liquid gallium jet-plasma interaction. A stable jet has been obtained, which was not noticeably affected by the magnetic field transients. ISTTOK has been successfully operated with the gallium jet without degradation of the discharge or a significant plasma contamination by liquid metal. This observation is supported by spectroscopic measurements showing that gallium radiation is limited to the region around the jet. Furthermore, the power deposited on the jet has been evaluated at different radial locations and the surface temperature increase estimated.

  18. Extremely-efficient, miniaturized, long-lived alpha-voltaic power source using liquid gallium

    NASA Technical Reports Server (NTRS)

    Snyder, G. Jeffrey (Inventor); Patel, Jagdishbhai (Inventor); Fleurial, Jean-Pierre (Inventor)

    2004-01-01

    A power source converts .alpha.-particle energy to electricity for use in electrical systems. Liquid gallium or other liquid medium is subjected to .alpha.-particle emissions. Electrons are freed by collision from neutral gallium atoms to provide gallium ions. The electrons migrate to a cathode while the gallium ions migrate to an anode. A current and/or voltage difference then arises between the cathode and anode because of the work function difference of the cathode and anode. Gallium atoms are regenerated by the receiving of electrons from the anode enabling the generation of additional electrons from additional .alpha.-particle collisions.

  19. On-chip superconductivity via gallium overdoping of silicon

    SciTech Connect

    Skrotzki, R.; Herrmannsdoerfer, T.; Heera, V.; Voelskow, M.; Muecklich, A.; Schmidt, B.; Skorupa, W.; Helm, M.; Wosnitza, J.; Fiedler, J.; Gobsch, G.

    2010-11-08

    We report on superconducting properties of gallium-enriched silicon layers in commercial (100) oriented silicon wafers. Ion implantation and subsequent rapid thermal annealing have been applied for realizing gallium precipitation beneath a silicon-dioxide cover layer. Depending on the preparation parameters, we observe a sharp drop to zero resistance at 7 K. The critical-field anisotropy proofs the thin-film character of superconductivity. In addition, out-of-plane critical fields of above 9 T and critical current densities exceeding 2 kA/cm{sup 2} promote these structures to be possible playgrounds for future microelectronic technology.

  20. First results from the Soviet-American Gallium Experiment

    SciTech Connect

    Abazov, A.I.; Abdurashitov, D.N.; Anosov, O.L.; Eroshkina, L.A.; Faizov, E.L.; Gavrin, V.N.; Kalikhov, A.V.; Knodel, T.V.; Knyshenko, I.I.; Kornoukhov, V.N.; Mezentseva, S.A.; Mirmov, I.N.; Ostrinsky, A.I.; Petukhov, V.V.; Pshukov, A.M.; Revzin, N.Y.; Shikhin, A.A.; Timofeyev, P.V.; Veretenkin, E.P.; Vermul, V.M.; Zakharov, Y.; Zatsepin, G.T.; Zhandarov, V.I. . Inst. Yadernykh Issledovanij); Bowl

    1990-01-01

    The Soviet-American Gallium Experiment is the first experiment able to measure the dominant flux of low energy p-p solar neutrinos. Four extractions made during January to May 1990 from 30 tons of gallium have been counted and indicate that the flux is consistent with 0 SNU and is less than 72 SNU (68% CL) and less than 138 SNU (95% CL). This is to be compared with the flux of 132 SNU predicted by the Standard Solar Model. 10 refs., 4 figs., 1 tab.

  1. Synthesis and characterization of inorganic-organic hybrid gallium selenides.

    PubMed

    Ewing, Sarah J; Vaqueiro, Paz

    2014-09-01

    Two semiconducting hybrid gallium selenides, [Ga6Se9(C6H14N2)4][H2O] (1) and [C6H14N2][Ga4Se6(C6H14N2)2] (2), were prepared using a solvothermal method in the presence of 1,2-diaminocyclohexane (1,2-DACH). Both materials consist of neutral inorganic layers, in which 1,2-DACH is covalently bonded to gallium. In 1, the organic amine acts as a monodentate and a bidentate ligand, while in 2, bidentate and uncoordinated 1,2-DACH molecules coexist. PMID:25113435

  2. Pseudomembranous colitis: a possible role for Gallium scanning

    SciTech Connect

    Kramer, E.L.; Charap, M.; Sanger, J.J.; Tiu, S.S.

    1983-10-01

    A case of antibiotic-associated pseudomembranous colitis is presented in which the Gallium scan was the first diagnostic modality to alert the clinicians to the existence of an inflammatory bowel process. The mechanism of localization of the radiopharmaceutical in inflammatory bowel disease is discussed. Although colonoscopy is far more specific and should be the first-line diagnostic tool used in assessing the presence of pseudomembranous colitis, Gallium scanning may have a role in the follow-up of treatment and in cases of relapse.

  3. Absence of gallium-67 avidity in diffuse pulmonary calcification

    SciTech Connect

    Lecklitner, M.L.; Foster, R.W.

    1985-09-01

    Diffuse pulmonary uptake by bone-seeking radiopharmaceuticals has been reported previously but, in the same patient, would pulmonary uptake of Ga-67 citrate yield clinically meaningful results. A patient with hypercalcemia and renal failure in whom bone scintigraphy demonstrated striking diffuse bilateral pulmonary uptake, but subsequent gallium imaging demonstrated no evidence of pulmonary uptake greater than body background, is discussed. We conclude that pulmonary uptake of gallium cannot be attributed to calcium deposition and should carry the same clinical significance in regard to inflammatory and malignant lesions as would be assigned to patients without pulmonary calcific deposits.

  4. Optical constants of thin-film gallium sulfide layers

    NASA Astrophysics Data System (ADS)

    Jenkins, Phillip; Tuma, Meg L.; Naghski, David H.; MacInnes, Andrew

    1996-03-01

    Gallium sulfide (GaS) deposited by chemical vapor deposition (CVD) is known to passivate GaAs surfaces. In this paper we examine the thin film optical properties of GaS as they relate to the fabrication of optical waveguides. Spectroscopic ellipsometry was used to determine the index of refraction of GaS films deposited on various substrates. Results indicate that GaS has a high index of refraction suitable for waveguide structures. A gallium sulfide waveguide could provide both the optical interconnect and the passivating layer of GaAs integrated circuits. Progress toward fabricating GaS waveguides is also discussed.

  5. Gallium arsenide processing for gate array logic

    NASA Technical Reports Server (NTRS)

    Cole, Eric D.

    1989-01-01

    The development of a reliable and reproducible GaAs process was initiated for applications in gate array logic. Gallium Arsenide is an extremely important material for high speed electronic applications in both digital and analog circuits since its electron mobility is 3 to 5 times that of silicon, this allows for faster switching times for devices fabricated with it. Unfortunately GaAs is an extremely difficult material to process with respect to silicon and since it includes the arsenic component GaAs can be quite dangerous (toxic) especially during some heating steps. The first stage of the research was directed at developing a simple process to produce GaAs MESFETs. The MESFET (MEtal Semiconductor Field Effect Transistor) is the most useful, practical and simple active device which can be fabricated in GaAs. It utilizes an ohmic source and drain contact separated by a Schottky gate. The gate width is typically a few microns. Several process steps were required to produce a good working device including ion implantation, photolithography, thermal annealing, and metal deposition. A process was designed to reduce the total number of steps to a minimum so as to reduce possible errors. The first run produced no good devices. The problem occurred during an aluminum etch step while defining the gate contacts. It was found that the chemical etchant attacked the GaAs causing trenching and subsequent severing of the active gate region from the rest of the device. Thus all devices appeared as open circuits. This problem is being corrected and since it was the last step in the process correction should be successful. The second planned stage involves the circuit assembly of the discrete MESFETs into logic gates for test and analysis. Finally the third stage is to incorporate the designed process with the tested circuit in a layout that would produce the gate array as a GaAs integrated circuit.

  6. Gallium arsenide processing for gate array logic

    NASA Astrophysics Data System (ADS)

    Cole, Eric D.

    1989-09-01

    The development of a reliable and reproducible GaAs process was initiated for applications in gate array logic. Gallium Arsenide is an extremely important material for high speed electronic applications in both digital and analog circuits since its electron mobility is 3 to 5 times that of silicon, this allows for faster switching times for devices fabricated with it. Unfortunately GaAs is an extremely difficult material to process with respect to silicon and since it includes the arsenic component GaAs can be quite dangerous (toxic) especially during some heating steps. The first stage of the research was directed at developing a simple process to produce GaAs MESFETs. The MESFET (MEtal Semiconductor Field Effect Transistor) is the most useful, practical and simple active device which can be fabricated in GaAs. It utilizes an ohmic source and drain contact separated by a Schottky gate. The gate width is typically a few microns. Several process steps were required to produce a good working device including ion implantation, photolithography, thermal annealing, and metal deposition. A process was designed to reduce the total number of steps to a minimum so as to reduce possible errors. The first run produced no good devices. The problem occurred during an aluminum etch step while defining the gate contacts. It was found that the chemical etchant attacked the GaAs causing trenching and subsequent severing of the active gate region from the rest of the device. Thus all devices appeared as open circuits. This problem is being corrected and since it was the last step in the process correction should be successful. The second planned stage involves the circuit assembly of the discrete MESFETs into logic gates for test and analysis. Finally the third stage is to incorporate the designed process with the tested circuit in a layout that would produce the gate array as a GaAs integrated circuit.

  7. Gallium-67 uptake by the thyroid associated with progressive systemic sclerosis

    SciTech Connect

    Sjoberg, R.J.; Blue, P.W.; Kidd, G.S.

    1989-01-01

    Although thyroidal uptake of gallium-67 has been described in several thyroid disorders, gallium-67 scanning is not commonly used in the evaluation of thyroid disease. Thyroidal gallium-67 uptake has been reported to occur frequently with subacute thyroiditis, anaplastic thyroid carcinoma, and thyroid lymphoma, and occasionally with Hashimoto's thyroiditis and follicular thyroid carcinoma. A patient is described with progressive systemic sclerosis who, while being scanned for possible active pulmonary involvement, was found incidentally to have abnormal gallium-67 uptake only in the thyroid gland. Fine needle aspiration cytology of the thyroid revealed Hashimoto's thyroiditis. Although Hashimoto's thyroiditis occurs with increased frequency in patients with progressive systemic sclerosis, thyroidal uptake of gallium-67 associated with progressive systemic sclerosis has not, to our knowledge, been previously described. Since aggressive thyroid malignancies frequently are imaged by gallium-67 scintigraphy, fine needle aspiration cytology of the thyroid often is essential in the evaluation of thyroidal gallium-67 uptake.

  8. Ferromagnetic shape memory alloys: structural and thermal properties

    NASA Astrophysics Data System (ADS)

    Suñol, J. J.; Escoda, L.; Coll, R.; Saurina, J.; Sánchez, T.; Prida, V. M.; Hernando, B.

    2010-11-01

    The most extensively studied Heusler alloys are those based on the Ni-Mn-Ga system. However, to overcome the high cost of Gallium and the usually low martensitic transformation temperature, the search for Ga-free alloys has been recently attempted, particularly, by introducing In, Sn or Sb. In this work, two alloys (Mn50Ni35.5In14.5 and Ni50Mn35In15) have been obtained by melt spinning. We outline their structural and thermal behaviour. Mn50Ni35.5In14.5 alloy has the transformation above room temperature whereas Ni50Mn35In15 does not have this transformation in the temperature range here analyzed.

  9. Radiant power degradation of silicon-doped gallium arsenide and gallium aluminum arsenide infrared light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Resimont, William N.

    1987-05-01

    This work investigates the use of the capacitance-voltage (C-V), current-voltage (I-V), and radiant power-current-voltage (P-I-V) diode characteristics as a means of modeling the general radiant power degradation of silicon-doped gallium arsenide and gallium aluminum arsenide (GaAs:Si, GaAlAs:Si) infrared light emmiting diodes. The procedure consists of measuring the initial characteristics, stressing with various operating current densities at room temperature, then periodically repeating the measurements. Control diodes that are not stressed are tested to determine the precision of the measuring apparatus and the normal variations in diode behavior.

  10. Synthesis of gallium nitride nanostructures by nitridation of electrochemically deposited gallium oxide on silicon substrate

    NASA Astrophysics Data System (ADS)

    Ghazali, Norizzawati Mohd; Yasui, Kanji; Hashim, Abdul Manaf

    2014-12-01

    Gallium nitride (GaN) nanostructures were successfully synthesized by the nitridation of the electrochemically deposited gallium oxide (Ga2O3) through the utilization of a so-called ammoniating process. Ga2O3 nanostructures were firstly deposited on Si substrate by a simple two-terminal electrochemical technique at a constant current density of 0.15 A/cm2 using a mixture of Ga2O3, HCl, NH4OH and H2O for 2 h. Then, the deposited Ga2O3 sample was ammoniated in a horizontal quartz tube single zone furnace at various ammoniating times and temperatures. The complete nitridation of Ga2O3 nanostructures at temperatures of 850°C and below was not observed even the ammoniating time was kept up to 45 min. After the ammoniating process at temperature of 900°C for 15 min, several prominent diffraction peaks correspond to hexagonal GaN (h-GaN) planes were detected, while no diffraction peak of Ga2O3 structure was detected, suggesting a complete transformation of Ga2O3 to GaN. Thus, temperature seems to be a key parameter in a nitridation process where the deoxidization rate of Ga2O3 to generate gaseous Ga2O increase with temperature. The growth mechanism for the transformation of Ga2O3 to GaN was proposed and discussed. It was found that a complete transformation can not be realized without a complete deoxidization of Ga2O3. A significant change of morphological structures takes place after a complete transformation of Ga2O3 to GaN where the original nanorod structures of Ga2O3 diminish, and a new nanowire-like GaN structures appear. These results show that the presented method seems to be promising in producing high-quality h-GaN nanostructures on Si.

  11. Characteristics of epitaxial garnets grown by CVD using single metal alloy sources. [Chemical Vapor Deposition

    NASA Technical Reports Server (NTRS)

    Besser, P. J.; Hamilton, T. N.; Mee, J. E.; Stermer, R. L.

    1974-01-01

    Single metal alloys have been explored as the cation source in the chemical vapor deposition (CVD) of iron garnets. Growth of good quality single crystal garnet films containing as many as five different cations has been achieved over a wide range of deposition conditions. The relationship of film composition to alloy compositions and deposition conditions has been determined for several materials. By proper choice of the alloy composition and the deposition conditions, uncrazed deposits were grown on (111) gadolinium gallium garnet (GGG) substrates. Data on physical, magnetic and optical properties of representative films is presented and discussed.

  12. Cellular uptake and anticancer activity of carboxylated gallium corroles.

    PubMed

    Pribisko, Melanie; Palmer, Joshua; Grubbs, Robert H; Gray, Harry B; Termini, John; Lim, Punnajit

    2016-04-19

    We report derivatives of gallium(III) tris(pentafluorophenyl)corrole, 1 [Ga(tpfc)], with either sulfonic (2) or carboxylic acids (3, 4) as macrocyclic ring substituents: the aminocaproate derivative, 3 [Ga(ACtpfc)], demonstrated high cytotoxic activity against all NCI60 cell lines derived from nine tumor types and confirmed very high toxicity against melanoma cells, specifically the LOX IMVI and SK-MEL-28 cell lines. The toxicities of 1, 2, 3, and 4 [Ga(3-ctpfc)] toward prostate (DU-145), melanoma (SK-MEL-28), breast (MDA-MB-231), and ovarian (OVCAR-3) cancer cells revealed a dependence on the ring substituent: IC50values ranged from 4.8 to >200 µM; and they correlated with the rates of uptake, extent of intracellular accumulation, and lipophilicity. Carboxylated corroles 3 and 4, which exhibited about 10-fold lower IC50values (<20 µM) relative to previous analogs against all four cancer cell lines, displayed high efficacy (Emax= 0). Confocal fluorescence imaging revealed facile uptake of functionalized gallium corroles by all human cancer cells that followed the order: 4 > 3 > 2 > 1 (intracellular accumulation of gallium corroles was fastest in melanoma cells). We conclude that carboxylated gallium corroles are promising chemotherapeutics with the advantage that they also can be used for tumor imaging. PMID:27044076

  13. Axial Distribution of Gallium in Silicon Crystals for Photovoltaic Applications

    NASA Astrophysics Data System (ADS)

    Lee, Kyoung-Hee

    2007-05-01

    The lifetime degradation induced by light illumination or carrier injection observed in Czochralski-grown silicon leads to a significant decrease in solar cell efficiency. The reduction in the extent of this effect has a high potential for the improvement of Czochralski-grown silicon solar cells. An approach to the substitution of boron with gallium in p-type Czochralski-grown silicon crystal has been pursued in a recent study. Since a reduced extent of light-induced degradation of minority carrier lifetime was observed, this approach seems to be very promising. The only disadvantage is the low segregation coefficient of gallium in silicon, resulting in a high resistivity variation over the crystal length compared with that in the case of boron doping. We propose a simple codoping (e.g., gallium and bismuth) method for controlling resistivity variation. Numerical simulations have been performed to study the transport phenomena of dopants in conventional and proposed silicon growth processes using the finite-element method and implicit Euler time integration. It has been demonstrated using mathematical models and numerical analysis that the axial distribution of effective gallium concentration can be modified in Czochralski-grown silicon for photovoltaic applications and made relatively uniform by the proposed doping method.

  14. The 100 micron detector development program. [gallium doped germanium photoconductors

    NASA Technical Reports Server (NTRS)

    Moore, W. J.

    1976-01-01

    An effort to optimize gallium-doped germanium photoconductors (Ge:Ga) for use in space for sensitive detection of far infrared radiation in the 100 micron region is described as well as the development of cryogenic apparatus capable of calibrating detectors under low background conditions.

  15. Discovery of gallium, germanium, lutetium, and hafnium isotopes

    SciTech Connect

    Gross, J.L.; Thoennessen, M.

    2012-09-15

    Currently, twenty-eight gallium, thirty-one germanium, thirty-five lutetium, and thirty-six hafnium isotopes have been observed and the discovery of these isotopes is described here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

  16. Field emission from gallium-doped zinc oxide nanofiber array

    NASA Astrophysics Data System (ADS)

    Xu, C. X.; Sun, X. W.; Chen, B. J.

    2004-03-01

    Gallium-doped nanostructural zinc oxide fibers have been fabricated by vapor-phase transport method of heating the mixture of zinc oxide, gallium oxide, and graphite powders in air. The zinc oxide fibers grew along [002] direction, forming a vertically aligned array that is predominantly perpendicular to the substrate surface. With a gallium doping concentration of 0.73 at. %, the corresponding carrier concentration and resistivity were 3.77×1020 cm-3 and 8.9×10-4 Ω cm, respectively. The field emission of these vertically aligned ZnO fiber arrays showed a low field emission threshold (2.4 V/μm at a current density of 0.1 μA/cm2), high current density, and high field enhancement factor (2317). The dependence of emission current density on the electric field followed Fowler-Nordheim relationship. The enhanced field emission is attributed to the aligned structure, good crystal quality, and especially, the improved electrical properties (increased conductivity and reduced work function) of the nanofibers due to gallium doping.

  17. Self- and zinc diffusion in gallium antimonide

    SciTech Connect

    Nicols, Samuel Piers

    2002-03-26

    The technological age has in large part been driven by the applications of semiconductors, and most notably by silicon. Our lives have been thoroughly changed by devices using the broad range of semiconductor technology developed over the past forty years. Much of the technological development has its foundation in research carried out on the different semiconductors whose properties can be exploited to make transistors, lasers, and many other devices. While the technological focus has largely been on silicon, many other semiconductor systems have applications in industry and offer formidable academic challenges. Diffusion studies belong to the most basic studies in semiconductors, important from both an application as well as research standpoint. Diffusion processes govern the junctions formed for device applications. As the device dimensions are decreased and the dopant concentrations increased, keeping pace with Moore's Law, a deeper understanding of diffusion is necessary to establish and maintain the sharp dopant profiles engineered for optimal device performance. From an academic viewpoint, diffusion in semiconductors allows for the study of point defects. Very few techniques exist which allow for the extraction of as much information of their properties. This study focuses on diffusion in the semiconductor gallium antimonide (GaSb). As will become clear, this compound semiconductor proves to be a powerful one for investigating both self- and foreign atom diffusion. While the results have direct applications for work on GaSb devices, the results should also be taken in the broader context of III-V semiconductors. Results here can be compared and contrasted to results in systems such as GaAs and even GaN, indicating trends within this common group of semiconductors. The results also have direct importance for ternary and quaternary semiconductor systems used in devices such as high speed InP/GaAsSb/InP double heterojunction bipolar transistors (DHBT) [Dvorak, (2001)]. Many of the findings which will be reported here were previously published in three journal articles. Hartmut Bracht was the lead author on two articles on self-diffusion studies in GaSb [Bracht, (2001), (2000)], while this report's author was the lead author on Zn diffusion results [Nicols, (2001)]. Much of the information contained herein can be found in those articles, but a more detailed treatment is presented here.

  18. Pair distribution function study on compression of liquid gallium

    NASA Astrophysics Data System (ADS)

    Yu, T.; Ehm, L.; Chen, J.; Guo, Q.; Luo, S.; Parise, J.

    2008-12-01

    Integrating a hydrothermal diamond anvil cell (HDAC) and focused high energy x-ray beam from the superconductor wiggler X17 beamline at the National Synchrotron Light Source (NSLS) at the Brookhaven National Laboratory (BNL), we have successfully collected high quality total x-ray scattering data of liquid gallium. The experiments were conducted at a pressure range from 0.1GPa up to 2GPa at ambient temperature. For the first time, pair distribution functions (PDF) for liquid gallium at high pressure were derived up to 10 Å. Liquid gallium structure has been studied by x-ray absorption (Di Cicco & Filipponi, 1993; Wei et al., 2000; Comez et al., 2001), x-ray diffraction studies (Waseda & Suzuki, 1972), and molecular dynamics simulation (Tsay, 1993; Hui et al., 2002). These previous reports have focused on the 1st nearest neighbor structure, which tells us little about the atomic arrangement outside the first shell in non- crystalline materials. This study focuses on the structure of liquid gallium and the atomic structure change due to compression. The PDF results show that the observed atomic distance of the first nearest neighbor at 2.78 Å (first G(r) peak and its shoulder at the higher Q position) is consistent with previous studies by x-ray absorption (2.76 Å, Comez et al., 2001). We have also observed that the first nearest neighbor peak position did not change with pressure increasing, while the farther peaks positions in the intermediate distance range decreased with pressure increasing. This leads to a conclusion of the possible existence of "locally rigid units" in the liquid. With the addition of reverse Monte Carlo modeling, we have observed that the coordination number in the local rigit unit increases with pressure. The bulk modulus of liquid gallium derived from the volume compression curve at ambient temperature (300K) is 12.1(6) GPa.

  19. Pair distribution function study on compression of liquid gallium

    SciTech Connect

    Luo, Shengnian; Yu, Tony; Chen, Jiuhua; Ehm, Lars; Guo, Quanzhong; Parise, John

    2008-01-01

    Integrating a hydrothermal diamond anvil cell (HDAC) and focused high energy x-ray beam from the superconductor wiggler X17 beamline at the National Synchrotron Light Source (NSLS) at the Brookhaven National Laboratory (BNL), we have successfully collected high quality total x-ray scattering data of liquid gallium. The experiments were conducted at a pressure range from 0.1GPa up to 2GPa at ambient temperature. For the first time, pair distribution functions (PDF) for liquid gallium at high pressure were derived up to 10 {angstrom}. Liquid gallium structure has been studied by x-ray absorption (Di Cicco & Filipponi, 1993; Wei et al., 2000; Comez et al., 2001), x-ray diffraction studies (Waseda & Suzuki, 1972), and molecular dynamics simulation (Tsay, 1993; Hui et al., 2002). These previous reports have focused on the 1st nearest neighbor structure, which tells us little about the atomic arrangement outside the first shell in non- crystalline materials. This study focuses on the structure of liquid gallium and the atomic structure change due to compression. The PDF results show that the observed atomic distance of the first nearest neighbor at 2.78 {angstrom} (first G(r) peak and its shoulder at the higher Q position) is consistent with previous studies by x-ray absorption (2.76 {angstrom}, Comez et al., 2001). We have also observed that the first nearest neighbor peak position did not change with pressure increasing, while the farther peaks positions in the intermediate distance range decreased with pressure increasing. This leads to a conclusion of the possible existence of 'locally rigid units' in the liquid. With the addition of reverse Monte Carlo modeling, we have observed that the coordination number in the local rigit unit increases with pressure. The bulk modulus of liquid gallium derived from the volume compression curve at ambient temperature (300K) is 12.1(6) GPa.

  20. Synthesis of gallium nitride nanostructures by nitridation of electrochemically deposited gallium oxide on silicon substrate

    PubMed Central

    2014-01-01

    Gallium nitride (GaN) nanostructures were successfully synthesized by the nitridation of the electrochemically deposited gallium oxide (Ga2O3) through the utilization of a so-called ammoniating process. Ga2O3 nanostructures were firstly deposited on Si substrate by a simple two-terminal electrochemical technique at a constant current density of 0.15 A/cm2 using a mixture of Ga2O3, HCl, NH4OH and H2O for 2 h. Then, the deposited Ga2O3 sample was ammoniated in a horizontal quartz tube single zone furnace at various ammoniating times and temperatures. The complete nitridation of Ga2O3 nanostructures at temperatures of 850°C and below was not observed even the ammoniating time was kept up to 45 min. After the ammoniating process at temperature of 900°C for 15 min, several prominent diffraction peaks correspond to hexagonal GaN (h-GaN) planes were detected, while no diffraction peak of Ga2O3 structure was detected, suggesting a complete transformation of Ga2O3 to GaN. Thus, temperature seems to be a key parameter in a nitridation process where the deoxidization rate of Ga2O3 to generate gaseous Ga2O increase with temperature. The growth mechanism for the transformation of Ga2O3 to GaN was proposed and discussed. It was found that a complete transformation can not be realized without a complete deoxidization of Ga2O3. A significant change of morphological structures takes place after a complete transformation of Ga2O3 to GaN where the original nanorod structures of Ga2O3 diminish, and a new nanowire-like GaN structures appear. These results show that the presented method seems to be promising in producing high-quality h-GaN nanostructures on Si. PMID:25593562

  1. Synthesis of gallium nitride nanostructures by nitridation of electrochemically deposited gallium oxide on silicon substrate.

    PubMed

    Ghazali, Norizzawati Mohd; Yasui, Kanji; Hashim, Abdul Manaf

    2014-01-01

    Gallium nitride (GaN) nanostructures were successfully synthesized by the nitridation of the electrochemically deposited gallium oxide (Ga2O3) through the utilization of a so-called ammoniating process. Ga2O3 nanostructures were firstly deposited on Si substrate by a simple two-terminal electrochemical technique at a constant current density of 0.15 A/cm(2) using a mixture of Ga2O3, HCl, NH4OH and H2O for 2 h. Then, the deposited Ga2O3 sample was ammoniated in a horizontal quartz tube single zone furnace at various ammoniating times and temperatures. The complete nitridation of Ga2O3 nanostructures at temperatures of 850°C and below was not observed even the ammoniating time was kept up to 45 min. After the ammoniating process at temperature of 900°C for 15 min, several prominent diffraction peaks correspond to hexagonal GaN (h-GaN) planes were detected, while no diffraction peak of Ga2O3 structure was detected, suggesting a complete transformation of Ga2O3 to GaN. Thus, temperature seems to be a key parameter in a nitridation process where the deoxidization rate of Ga2O3 to generate gaseous Ga2O increase with temperature. The growth mechanism for the transformation of Ga2O3 to GaN was proposed and discussed. It was found that a complete transformation can not be realized without a complete deoxidization of Ga2O3. A significant change of morphological structures takes place after a complete transformation of Ga2O3 to GaN where the original nanorod structures of Ga2O3 diminish, and a new nanowire-like GaN structures appear. These results show that the presented method seems to be promising in producing high-quality h-GaN nanostructures on Si. PMID:25593562

  2. Keeping gallium metal to liquid state under the freezing point by using silica nanoparticles

    NASA Astrophysics Data System (ADS)

    Cao, Lingfei; Park, Hyunseo; Dodbiba, Gjergj; Ono, Kenji; Tokoro, Chiharu; Fujita, Toyohisa

    2011-10-01

    Gallium metal under the freezing point was observed to maintain its liquid state by dispersing silica nanoparticles of a given particle size and concentration. Though the freezing point of pure gallium is 302.9 K, the liquid gallium maintained its supercooling state at 276-277 K for more than 400 days by dispersing 1.0 wt. % of silica nanoparticles (10 nm in size). Extended x-ray absorption fine structure analysis shows that the supercooled gallium liquid has a β-Ga-like feature, and the nearest neighboring atom distance is 0.1 Å larger than that of pure liquid gallium. This method opens the way to use liquid gallium as a promising fluid carrier in energy conversion devices.

  3. Brittle-to-ductile transition in polycrystalline aluminum containing gallium in the grain boundaries

    NASA Astrophysics Data System (ADS)

    Itoh, A.; Izumi, J.; Ina, K.; Koizumi, H.

    2010-07-01

    It is well known that aluminum/gallium couple causes liquid metal embrittlement. Gallium atoms penetrate the grain boundaries of polycrystalline aluminum and degrade it. Polycrystalline aluminum specimens were contacted with a small droplet of gallium for 24 h. After gallium was removed from the surface of the specimens, tensile tests were performed between 77 K and 313 K. The specimens are ductile below 230 K and brittle above 303 K, the melting temperature of gallium. Between 280 K and 300 K, the maximum stress is larger in the specimens heated from 77 K than in those cooled from 313 K. This thermal history dependence of the maximum stress is considered to be attributed to the solidification of supercooled gallium in the grain boundaries.

  4. Vapor-phase epitaxy of gallium nitride by gallium arc discharge evaporation

    NASA Astrophysics Data System (ADS)

    Heikman, S.; Keller, S.; Mishra, U. K.

    2006-08-01

    Vapor-phase epitaxy of GaN was performed by combining ammonia with gallium evaporated into an inert gas stream by a DC arc discharge, and letting the mixture pass through a pair of heated graphite susceptors. Growth rates as high as 30 ?m/h were achieved. The growth on the top sample was specular in a large area, and was of high quality as characterized by atomic force microscopy and photoluminescence spectroscopy. The bottom sample had a high density of macroscopic defects, presumably caused by Ga droplets in the gas phase resulting from the arc evaporation process. The experimental growth rate was found to be less than {1}/{3} of values predicted in a computer flow dynamic model of the growth system, and Ga-NH 3 pre-reactions were implicated as the likely cause of the discrepancy. The growth efficiency, calculated to 2%, could arguably be improved by reducing the reactor growth pressure, and by changing the reactor geometry to avoid Ga condensation on walls. Potential advantages of the described growth technique are cheap source materials of high purity and low equipment costs. Furthermore, since no corrosive gasses were used, hardware corrosion and gas-phase impurities can be reduced.

  5. ''Hot spot'' on gallium-67-citrate scan in renal cell carcinoma. Clinicopathologic and biochemical correlation

    SciTech Connect

    Kawamura, J.; Itoh, H.; Yoshida, O.; Fujita, T.; Torizuka, K.

    1984-09-01

    A frontal tomographic whole-body gallium-67-citrate scan was performed on 30 patients with renal cell carcinoma. Positive gallium uptake by the kidney in 20 patients (66.7%) correlated well with the clinicopathologically higher stage and grade of the tumor and with abnormal values in prognostic indexes in the blood. Thus, a negative gallium uptake may be indicative of an improved clinical course and longer survival in patients with renal cell carcinoma.

  6. Gallium uptake in the thyroid gland in amiodarone-induced hyperthyroidism

    SciTech Connect

    Ling, M.C.; Dake, M.D.; Okerlund, M.D.

    1988-04-01

    Amiodarone is an iodinated antiarrhythmic agent that is effective in the treatment of atrial and ventricular arrhythmias. A number of side effects are seen, including pulmonary toxicity and thyroid dysfunction. A patient with both amiodarone-induced pneumonitis and hyperthyroidism who exhibited abnormal gallium activity in the lungs, as well as diffuse gallium uptake in the thyroid gland is presented. The latter has not been previously reported and supports the concept of iodide-induced thyroiditis with gallium uptake reflecting the inflammatory response.

  7. VANADIUM ALLOYS

    DOEpatents

    Smith, K.F.; Van Thyne, R.J.

    1959-05-12

    This patent deals with vanadium based ternary alloys useful as fuel element jackets. According to the invention the ternary vanadium alloys, prepared in an arc furnace, contain from 2.5 to 15% by weight titanium and from 0.5 to 10% by weight niobium. Characteristics of these alloys are good thermal conductivity, low neutron capture cross section, good corrosion resistance, good welding and fabricating properties, low expansion coefficient, and high strength.

  8. BRAZING ALLOYS

    DOEpatents

    Donnelly, R.G.; Gilliland, R.G.; Slaughter, G.M.

    1963-02-26

    A brazing alloy which, in the molten state, is characterized by excellent wettability and flowability, said alloy being capable of forming a corrosion resistant brazed joint wherein at least one component of said joint is graphite and the other component is a corrosion resistant refractory metal, said alloy consisting essentially of 20 to 50 per cent by weight of gold, 20 to 50 per cent by weight of nickel, and 15 to 45 per cent by weight of molybdenum. (AEC)

  9. Cutaneous gallium uptake in patients with AIDS with mycobacterium avium-intracellulare septicemia

    SciTech Connect

    Allwright, S.J.; Chapman, P.R.; Antico, V.F.; Gruenewald, S.M.

    1988-07-01

    Gallium imaging is increasingly being used for the early detection of complications in patients with AIDS. A 26-year-old homosexual man who was HIV antibody positive underwent gallium imaging for investigation of possible Pneumocystis carinii pneumonia. Widespread cutaneous focal uptake was seen, which was subsequently shown to be due to mycobacterium avium-intracellulare (MAI) septicemia. This case demonstrates the importance of whole body imaging rather than imaging target areas only, the utility of gallium imaging in aiding the early detection of clinically unsuspected disease, and shows a new pattern of gallium uptake in disseminated MAI infection.

  10. The efficacy of gallium scintigraphy in detecting malignant soft tissue neoplasms.

    PubMed Central

    Schwartz, H S; Jones, C K

    1992-01-01

    A prospective study was conducted on 55 consecutive patients to evaluate the efficacy of gallium scintigraphy in detecting malignancy in any soft tissue mass. It was determined that gallium scintigraphy could detect malignancy with a sensitivity of 96% and a specificity of 87%. Large and small sarcomas, irrespective of their fascial location, were identifiable by gallium imaging. Occult, nonpulmonary sites of disseminated disease were detected in 13%. Gallium scintigraphy proved to be a reliable predictor of malignancy for all soft tissue masses, but because of its cost, it must be used judiciously. Images FIG. 1. FIG. 2. PMID:1731652

  11. Nonpolar m-plane gallium Nitride-based Laser Diodes in the Blue Spectrum

    NASA Astrophysics Data System (ADS)

    Kelchner, Kathryn M.

    Gallium nitride (GaN), together with its alloys with aluminum and indium, have revolutionized the solid-state optoelectronics market for their ability to emit a large portion of the visible electromagnetic spectrum from deep ultraviolet and into the infrared. GaN-based semiconductor laser diodes (LDs) with emission wavelengths in the violet, blue and green are already seeing widespread implementation in applications ranging from energy storage, lighting and displays. However, commercial GaN-based LDs use the basal c-plane orientation of the wurtzite crystal, which can suffer from large internal electric fields due to discontinuities in spontaneous and piezoelectric polarizations, limiting device performance. The nonpolar orientation of GaN benefits from the lack of polarization-induced electric field as well as enhanced gain. This dissertation discusses some of the benefits and limitations of m-plane oriented nonpolar GaN for LD applications in the true blue spectrum (450 nm). Topics include an overview of material growth by metal-organic chemical vapor deposition (MOCVD), waveguide design and processing techniques for improving device performance for multiple lateral mode and single lateral mode ridge waveguides.

  12. Fabrication and optical properties of gallium phosphide nanoparticulate thin film

    NASA Astrophysics Data System (ADS)

    Wang, Bao-Ping; Zhang, Zhao-Chun; Zhang, Neng

    2010-07-01

    The gallium phosphide (GaP) nanoparticulate thin films were fabricated by colloidal suspensions deposition with GaP nanoparticles dispersed in N, N-dimethylformamide (DMF). The microstructure and optical properties of the film have been studied by scanning electron microscopy, high resolution transmission electron microscope, and optical absorption and fluorescence spectra. The morphology of the film was found to be composed of nanoparticle aggregates, and with an irregularly rough surface. From the result of fluorescence, it can be established that the film not only retains the violet and blue light emissions which ascribed to transition from conduction band to valence band of gallium phosphide particles, but has an excellent luminescence property. The correlation between the optical properties and the microstructure of the thin film is discussed.

  13. Usefulness of gallium imaging in the evaluation of lung cancer

    SciTech Connect

    Alazraki, N.

    1980-01-01

    The current enthusiasm for gallium (Ga) citrate as a tumor imaging agent reflects the need of clinical medicine for a good tumor imaging agent. Ga-67 was most consistently and reliably taken up in lung tumors, with sensitivities of Ga imaging positivity in lung cancer ranging from 85 to 95%. Subsequent studies on Ga-67 led to the recognition of its preferential concentration in inflammatory lesions and abscess. These reports resulted in the clinical application of Ga-67 imaging as a diagnostic tool in the evaluation of patients with suspected abscesses. Mechanisms of Ga localization in tumor and inflammatory lesions are not currently well understood. Data regarding the thresholds of various factors which determine visibility of a lung tumor by Ga-67 imaging have been described in some detail. The factors include lesion size, depth in tissue, gallium concentration in tumor relative to background, type of film and instrumentation used, and count rates obtained.

  14. Detection of postcardiotomy bacterial pericarditis with gallium-67 citrate

    SciTech Connect

    Zuckier, L.S.; Weissmann, H.S.; Goldman, M.J.; Brodman, R.; Kamholz, S.L.; Freeman, L.M.

    1986-04-01

    A 46-year-old man who had undergone apical cardiac aneurysmectomy with a ventriculotomy graft and implanted automatic cardioverter-defibrillator electrodes, presented with fever, left-sided pleuritic chest pain, and a draining sinus. A Ga-67 scan was performed to aid in determining whether the infection was limited to the chest wall or if it had penetrated deeper to the cardiac structures. Uptake of gallium within the cardiac region, in association with minimal rib uptake of Tc-99m MDP, strongly supported the existence of infection within the pericardium. CT scan demonstrated a pericardial collection which under CT-guided aspiration proved to be purulent. Definitive surgical drainage was performed, and the patient was discharged 4 weeks postoperatively. Ga-67 imaging can provide an accurate and relatively rapid means of localizing infection in the postcardiotomy patient. A thorough bibliography of pericardial gallium uptake is provided.

  15. Vapor-Phase Synthesis of Gallium Phosphide Nanowires

    SciTech Connect

    Gu, Dr Zhanjun; Paranthaman, Mariappan Parans; Pan, Zhengwei

    2009-01-01

    Gallium phosphide (GaP) nanowires were synthesized in a high yield by vapor-phase reaction of gallium vapor and phosphorus vapor at 1150 C in a tube furnace system. The nanowires have diameters in the range of 25-100 nm and lengths of up to tens of micrometers. Twinning growth occurs in GaP nanowires, and as a result most nanowires contain a high density of twinning faults. Novel necklacelike GaP nanostructures that were formed by stringing tens of amorphous Ga-P-O microbeads upon one crystalline GaP nanowires were also found in some synthesis runs. This simple vapor-phase approach may be applied to synthesize other important group III-V compound nanowires.

  16. Preparation Of Copper Indium Gallium Diselenide Films For Solar Cells

    DOEpatents

    Bhattacharya, Raghu N.; Contreras, Miguel A.; Keane, James; Tennant, Andrew L. , Tuttle, John R.; Ramanathan, Kannan; Noufi, Rommel

    1998-08-08

    High quality thin films of copper-indium-gallium-diselenide useful in the production of solar cells are prepared by electrodepositing at least one of the constituent metals onto a glass/Mo substrate, followed by physical vapor deposition of copper and selenium or indium and selenium to adjust the final stoichiometry of the thin film to approximately Cu(In,Ga)Se.sub.2. Using an AC voltage of 1-100 KHz in combination with a DC voltage for electrodeposition improves the morphology and growth rate of the deposited thin film. An electrodeposition solution comprising at least in part an organic solvent may be used in conjunction with an increased cathodic potential to increase the gallium content of the electrodeposited thin film.

  17. Gallium nitride thick layers: Epitaxial growth and separation from substrates

    SciTech Connect

    Bel`kov, V.V.; Botnaryuk, V.M.; Fedorov, L.M.; Diakonu, I.I.; Krivolapchyuk, V.V.; Scheglov, M.P.; Zhilyaev, Yu.V.

    1997-12-31

    The authors investigated the possibilities of vapor phase epitaxy in an open tube chloride system for thick GaN film deposition on sapphire substrates. The methods of the buffer layer deposition were proposed and developed. The methods of fast (up to 100 microns/hour) was developed. Parameters of good quality gallium nitride epitaxy were obtained. To determine the quality of fast grown epitaxial layers they used X-ray diffraction and photoluminescence measurements. The halfwidth of the rocking curve for the best samples was equal to /4--6 minutes. Luminescence spectrum (T = 77K) had a maximum near 3.46 eV. A signal in the visible wavelength range was hardly observed. Polished layers were transparent. A special initial treatment of the substrates allowed them to separate thick (up to 300 micron) epitaxial gallium nitride layers from sapphire. It was shown that it is possible to use separated films for homoepitaxy of GaN.

  18. Thermodynamic properties of liquid gallium from picosecond acoustic velocity measurements

    NASA Astrophysics Data System (ADS)

    Ayrinhac, S.; Gauthier, M.; Le Marchand, G.; Morand, M.; Bergame, F.; Decremps, F.

    2015-07-01

    Due to discrepancies in the literature data the thermodynamic properties of liquid gallium are still in debate. Accurate measurements of adiabatic sound velocities as a function of pressure and temperature have been obtained by the combination of laser picosecond acoustics and surface imaging on sample loaded in diamond anvil cell. From these results the thermodynamic parameters of gallium have been extracted by a numerical procedure up to 10 GPa and 570 K. It is demonstrated that a Murnaghan equation of state accounts well for the whole data set since the isothermal bulk modulus BT has been shown to vary linearly with pressure in the whole temperature range. No evidence for a previously reported liquid-liquid transition has been found in the whole pressure and temperature range explored.

  19. Neutron detection using boron gallium nitride semiconductor material

    SciTech Connect

    Atsumi, Katsuhiro; Inoue, Yoku; Nakano, Takayuki; Mimura, Hidenori; Aoki, Toru

    2014-03-01

    In this study, we developed a new neutron-detection device using a boron gallium nitride (BGaN) semiconductor in which the B atom acts as a neutron converter. BGaN and gallium nitride (GaN) samples were grown by metal organic vapor phase epitaxy, and their radiation detection properties were evaluated. GaN exhibited good sensitivity to α-rays but poor sensitivity to γ-rays. Moreover, we confirmed that electrons were generated in the depletion layer under neutron irradiation. This resulted in a neutron-detection signal after α-rays were generated by the capture of neutrons by the B atoms. These results prove that BGaN is useful as a neutron-detecting semiconductor material.

  20. Thermal modeling of power gallium arsenide microwave integrated circuits

    SciTech Connect

    Webb, P.W. )

    1993-05-01

    Low-power Gallium Arsenide-based microwave circuits have been used for many years for frequencies higher than those possible with silicon technology. At the present time manufacturers are developing power devices for ever higher frequencies using GaAs MESFET's and heterojunction bipolar devices constructed with III-V compounds on GaAs substrates. There is also interest in integrating power devices on Monolithic Microwave Integrated Circuits (MMIC's). A problem with the technology is the low thermal conductivity of Gallium Arsenide and this gives rise to thermal design problems which must be solved if good reliability is to be achieved. The paper uses a three-dimensional numerical simulator to study this problem and in particular examines the approximations which are possible in performing realistic assessments of the thermal resistance of typical GaAs power device structures under steady-state conditions.

  1. Ultra-low threshold gallium nitride photonic crystal nanobeam laser

    SciTech Connect

    Niu, Nan Woolf, Alexander; Wang, Danqing; Hu, Evelyn L.; Zhu, Tongtong; Oliver, Rachel A.; Quan, Qimin

    2015-06-08

    We report exceptionally low thresholds (9.1 μJ/cm{sup 2}) for room temperature lasing at ∼450 nm in optically pumped Gallium Nitride (GaN) nanobeam cavity structures. The nanobeam cavity geometry provides high theoretical Q (>100 000) with small modal volume, leading to a high spontaneous emission factor, β = 0.94. The active layer materials are Indium Gallium Nitride (InGaN) fragmented quantum wells (fQWs), a critical factor in achieving the low thresholds, which are an order-of-magnitude lower than obtainable with continuous QW active layers. We suggest that the extra confinement of photo-generated carriers for fQWs (compared to QWs) is responsible for the excellent performance.

  2. Electrophysical properties of epitaxial gallium arsenide doped with acceptor impurities

    NASA Astrophysics Data System (ADS)

    Vilisova, M. D.; Kataev, Yu. G.; Chernov, N. A.; Bobrovnikova, I. A.; Teterkina, I. V.; Lavrent'eva, L. G.

    1995-02-01

    Epitaxial layers of gallium arsenide doped with zinc and cadmium were grown in a chloride vapor-transport system using diethylzinc and dimethylcadmium as the sources of the impurity. We studied the effect of the inlet pressure of the impurities and the growth temperature on the doping level of the layers. We investigated the temperature dependences of the hole concentration and mobility in layers doped with zinc and cadmium up to different levels.

  3. Terahertz Cherenkov radiation from ultrafast magnetization in terbium gallium garnet

    NASA Astrophysics Data System (ADS)

    Gorelov, S. D.; Mashkovich, E. A.; Tsarev, M. V.; Bakunov, M. I.

    2013-12-01

    We report an experimental observation of terahertz Cherenkov radiation from a moving magnetic moment produced in terbium gallium garnet by a circularly polarized femtosecond laser pulse via the inverse Faraday effect. Contrary to some existing theoretical predictions, the polarity of the observed radiation unambiguously demonstrates the paramagnetic, rather than diamagnetic, nature of the ultrafast inverse Faraday effect. From measurements of the radiation field, the Verdet constant in the subpicosecond regime is ˜3-10 times smaller than its table quasistatic value.

  4. Use of Gallium-67 in the diagnosis of occult infections

    SciTech Connect

    Hoffer, P.B.

    1981-05-01

    The mechanism of Ga-67 citrates in the diagnosis of infection involves the rapid binding of gallium by transferrin. The Ga-67-transferrin complex gains access into inflammatory tissue to some extent through the leaky endothelium of vessels at sites of inflammation. In addition, Ga-67 binds to a limited extent to circulating neutrophils. Advances in imaging techniques using Ga-67 citrates are discussed. The clinical applications include the diagnosis of bone and joint infections, pulmonary lesions, and infections of the urinary tract.

  5. Radiation-induced metastable ordered phase in gallium nitride

    SciTech Connect

    Ishimaru, Manabu

    2010-05-10

    Energetic particle irradiation is one of the useful ways for realizing metastable phases far from the equilibrium state. In the present study, we performed electron-beam-irradiation into gallium nitride (GaN) with a wurtzite structure and examined its structural changes using transmission electron microscopy. It was found that superlattice Bragg reflections appear in the electron diffraction patterns of the irradiated GaN. This suggests that the wurtzite GaN transforms to another crystalline structure with atomic ordering.

  6. Diagnosis of mycotic abdominal aortic aneurysm using 67-gallium citrate

    SciTech Connect

    Blumoff, R.L.; McCartney, W.; Jaques, P.; Johnson, G. Jr.

    1982-11-01

    Mycotic aneurysms of the abdominal aorta are uncommon, but potentially lethal problems. Clinical subtleties may suggest their presence, but in the past, definitive diagnosis has been dependent on surgical exploration or autopsy findings. A case is presented in which 67-gallium citrate abdominal scanning localized the site of sepsis in an abdominal aortic aneurysm and allowed for prompt and successful surgical therapy. This noninvasive technique is recommended as a adjunct in the diagnosis of mycotic abdominal aortic aneurysms.

  7. Indium, tin, and gallium doped cadmium selenide quantum dots

    NASA Astrophysics Data System (ADS)

    Tuinenga, Christopher J.

    Doping quantum dots to increase conductivity is a crucial step towards being able to fabricate a new generation of electronic devices built on the "bottom-up" platform that are smaller and more efficient than currently available. Indium, tin, and gallium have been used to dope CdSe in both the bulk and thin film regimes and introduce n-type electron donation to the conduction band. CdSe quantum dots have been successfully doped with indium, tin, and gallium using the Li4[Cd10Se4 (SPh16)] single source precursor combined with metal chloride compounds. Doping CdSe quantum dots is shown to effect particle growth dynamics in the "heterogeneous growth regime." Doping with indium, tin, and gallium introduce donor levels 280, 100, and 50 meV below the conduction band minimum, respectively. Thin films of indium and tin doped quantum dots show improved conductivity over films of undoped quantum dots. Transient Absorption spectroscopy indicates that indium doping introduces a new electron energy level in the conduction band that results in a 70 meV blue shift in the 1Se absorption bleach position. Novel characterization methods such as in-situ fluorescence growth monitoring, single quantum dot EDS acquisition, static and time-resolved temperature dependant fluorescence spectroscopy were developed in the course of this work as well. These results show that doping CdSe quantum dots with indium, tin, and gallium has not only been successful but has introduced new electronic properties to the quantum dots that make them superior to traditional CdSe quantum dots.

  8. Assessment of arsenic exposures and controls in gallium arsenide production.

    PubMed

    Sheehy, J W; Jones, J H

    1993-02-01

    The electronics industry is expanding the use of gallium arsenide in the production of optoelectronic devices and integrated circuits. Workers in the electronics industry using gallium arsenide are exposed to hazardous substances such as arsenic, arsine, and various acids. Arsenic requires stringent controls to minimize exposures (the current OSHA PEL for arsenic is 10 micrograms/m3 and the NIOSH REL is 2 micrograms/m3 ceiling). Inorganic arsenic is strongly implicated in respiratory tract and skin cancer. For these reasons, NIOSH researchers conducted a study of control systems for facilities using gallium arsenide. Seven walk-through surveys were performed to identify locations for detailed study which appeared to have effective controls; three facilities were chosen for in-depth evaluation. The controls were evaluated by industrial hygiene sampling. Including personal breathing zone and area air sampling for arsenic and arsine; wipe samples for arsenic also were collected. Work practices and the use of personal protective equipment were documented. This paper reports on the controls and the arsenic exposure results from the evaluation of the following gallium arsenide processes: Liquid Encapsulated Czochralski (LEC) and Horizontal Bridgeman (HB) crystal growing, LEC cleaning operations, ingot grinding/wafer sawing, and epitaxy. Results at one plant showed that in all processes except epitaxy, average arsenic exposures were at or above the OSHA action level of 5 micrograms/m3. While cleaning the LEC crystal pullers, the average potential arsenic exposure of the cleaning operators was 100 times the OSHA PEL. At the other two plants, personal exposures for arsenic were well controlled in LEC, LEC cleaning, grinding/sawing, and epitaxy operations. PMID:8452098

  9. Incidental diagnosis of pregnancy on bone and gallium scintigraphy

    SciTech Connect

    Palestro, C.J.; Malat, J.; Collica, C.J.; Richman, A.H.

    1986-03-01

    Bone and gallium scintigraphy were performed as part of the diagnostic workup of a 21-yr-old woman who presented at our institution with a history of progressively worsening low back pain over a 1-wk period of time. The angiographic phase of the bone scan demonstrated a well-defined radionuclide blush within the pelvis just cephalad to the urinary bladder with persistent hyperemia noted in the blood-pool image. We attribute these findings to a uterine blush secondary to the pronounced uterine muscular hyperplasia, hyperemia, and edema that accompany pregnancy. Gallium scintigraphy demonstrated intense bilateral breast accumulation of the imaging agent in a typical doughnut pattern which is commonly found in the prelactating and lactating breast. Also demonstrated was apparent gallium accumulation in the placenta. This case is presented to emphasize the radionuclide findings that occur during pregnancy, particularly the incidental finding of radionuclide blush during the angiographic phase of a radionuclide scintigraphy which should alert the nuclear physician to the possibility of pregnancy in a woman of childbearing age.

  10. Appraisal of lupus nephritis by renal imaging with gallium-67

    SciTech Connect

    Bakir, A.A.; Lopez-Majano, V.; Hryhorczuk, D.O.; Rhee, H.L.; Dunea, G.

    1985-08-01

    To assess the activity of lupus nephritis, 43 patients with systemic lupus erythematosus (SLE) were studied by gallium imaging. Delayed renal visualization 48 hours after the gallium injection, a positive result, was noted in 25 of 48 scans. Active renal disease was defined by the presence of hematuria, pyuria (10 or more red blood cells or white blood cells per high-power field), proteinuria (1 g or more per 24 hours), a rising serum creatinine level, or a recent biopsy specimen showing proliferative and/or necrotizing lesions involving more than 20 percent of glomeruli. Renal disease was active in 18 instances, inactive in 23, and undetermined in seven (a total of 48 scans). Sixteen of the 18 scans (89 percent) in patients with active renal disease showed positive findings, as compared with only four of 23 scans (17 percent) in patients with inactive renal disease (p less than 0.001). Patients with positive scanning results had a higher rate of hypertension (p = 0.02), nephrotic proteinuria (p = 0.01), and progressive renal failure (p = 0.02). Mild mesangial nephritis (World Health Organization classes I and II) was noted only in the patients with negative scanning results (p = 0.02) who, however, showed a higher incidence of severe extrarenal SLE (p = 0.04). It is concluded that gallium imaging is a useful tool in evaluating the activity of lupus nephritis.

  11. Defects in gallium nitride nanowires: first principles calculations

    SciTech Connect

    Wang, Zhiguo; Li, Jingbo; Gao, Fei; Weber, William J.

    2010-08-15

    Atomic configurations and formation energies of native defects in an unsaturated GaN nanowire grown along the [001] direction and with (100) lateral facets are studied using large-scale ab initio calculation. Cation and anion vacancies, antisites and interstitials in the neutral charge state are all considered. The nitrogen related defects are more stable than the gallium related defects under nitrogen-rich conditions. The configurations of these defects in the core region of the nanowire are same as those in the bulk GaN. The relaxation of vacancies is generally small, but the relaxation around antisite defects is large. The nitrogen interstitial relaxes into a split interstitial configuration. The configurations of the defects in the outermost free surface region are different than those in the core. A Ga atom on the outmost surface is replaced by a Ga interstital, and is ejected on to the surface to become an adsorbed atom. A gallium atom at the outermost surface can also be ejected out to become an adsorbed atom. Nitrogen interstitials form a split-interstitial configuration with one of the nearest-neighbor nitrogens. For a Ga vacancy at the edge of the side plane of the nanowire, nitrogen atom at a gallium site and nitrogen interstitial often induced the formation of N2 molecules with low formation energy, which agrees well with experiment findings [Nano Letters 9, 1844 (2009)].

  12. Corrosion of alloy 718 in a mercury thermal convection loop

    SciTech Connect

    Pawel, S.J.; DiStefano, J.R.; Manneschmidt, E.T.

    1999-12-01

    Two thermal convection loops (TCLs) fabricated from annealed alloy 718 continuously circulated mercury (Hg) with 1000 wppm gallium (Ga), respectively, for about 5000 h, duplicating previous TCL tests for annealed 316L. In each case, the maximum loop temperature was 305C, the minimum temperature was 242C, and the Hg flow rate was approximately 1.2 m/min. Unlike the 316L exposed to Hg, which above about 260C exhibited a thin, porous surface layer depleted in Ni and Cr, the alloy 718 coupons revealed essentially no wetting and, therefore, no interaction with that Hg at any temperature. Alloy 718 coupons suspended in the loops revealed inconsequentially small weight changes, and both the coupons and loop tubing exhibited no detectable metallographic evidence of attack.

  13. NiAl alloys for high-temperature structural applications

    NASA Astrophysics Data System (ADS)

    Darolia, Ram

    1991-03-01

    If their properties can be improved, nickel aluminide alloys offer significant payoffs in gas turbine engine applications. For these materials, excellent progress has been made toward understanding their mechanical behavior as well as improving their low-temperature ductility and high-temperature strength. For example, recent work shows that room-temperature ductility can be improved dramatically by microalloying with iron, gallium or molybdenum. The next challenge is to develop an alloy which has the required balance of ductility, toughness and strength. Development of design and test methodologies for components made out of low-ductility, anisotropic materials will also be required. While significant challenges remain, the continuing developments suggest that the prognosis for using NiAl alloys as high-temperature structural materials is good.

  14. Smooth cubic commensurate oxides on gallium nitride

    NASA Astrophysics Data System (ADS)

    Paisley, Elizabeth A.; Gaddy, Benjamin E.; LeBeau, James M.; Shelton, Christopher T.; Biegalski, Michael D.; Christen, Hans M.; Losego, Mark D.; Mita, Seiji; Collazo, Ramón; Sitar, Zlatko; Irving, Douglas L.; Maria, Jon-Paul

    2014-02-01

    Smooth, commensurate alloys of ⟨111⟩-oriented Mg0.52Ca0.48O (MCO) thin films are demonstrated on Ga-polar, c+ [0001]-oriented GaN by surfactant-assisted molecular beam epitaxy and pulsed laser deposition. These are unique examples of coherent cubic oxide|nitride interfaces with structural and morphological perfection. Metal-insulator-semiconductor capacitor structures were fabricated on n-type GaN. A comparison of leakage current density for conventional and surfactant-assisted growth reveals a nearly 100× reduction in leakage current density for the surfactant-assisted samples. HAADF-STEM images of the MCO|GaN interface show commensurate alignment of atomic planes with minimal defects due to lattice mismatch. STEM and DFT calculations show that GaN c/2 steps create incoherent boundaries in MCO over layers which manifest as two in-plane rotations and determine consequently the density of structural defects in otherwise coherent MCO. This new understanding of interfacial steps between HCP and FCC crystals identifies the steps needed to create globally defect-free heterostructures.

  15. Smooth cubic commensurate oxides on gallium nitride

    SciTech Connect

    Paisley, Elizabeth A.; Gaddy, Benjamin E.; LeBeau, James M.; Shelton, Christopher T.; Losego, Mark D.; Mita, Seiji; Collazo, Ramón; Sitar, Zlatko; Irving, Douglas L.; Maria, Jon-Paul; Biegalski, Michael D.; Christen, Hans M.

    2014-02-14

    Smooth, commensurate alloys of 〈111〉-oriented Mg{sub 0.52}Ca{sub 0.48}O (MCO) thin films are demonstrated on Ga-polar, c+ [0001]-oriented GaN by surfactant-assisted molecular beam epitaxy and pulsed laser deposition. These are unique examples of coherent cubic oxide|nitride interfaces with structural and morphological perfection. Metal-insulator-semiconductor capacitor structures were fabricated on n-type GaN. A comparison of leakage current density for conventional and surfactant-assisted growth reveals a nearly 100× reduction in leakage current density for the surfactant-assisted samples. HAADF-STEM images of the MCO|GaN interface show commensurate alignment of atomic planes with minimal defects due to lattice mismatch. STEM and DFT calculations show that GaN c/2 steps create incoherent boundaries in MCO over layers which manifest as two in-plane rotations and determine consequently the density of structural defects in otherwise coherent MCO. This new understanding of interfacial steps between HCP and FCC crystals identifies the steps needed to create globally defect-free heterostructures.

  16. Generalized stacking fault energies of alloys.

    PubMed

    Li, Wei; Lu, Song; Hu, Qing-Miao; Kwon, Se Kyun; Johansson, Börje; Vitos, Levente

    2014-07-01

    The generalized stacking fault energy (γ surface) provides fundamental physics for understanding the plastic deformation mechanisms. Using the ab initio exact muffin-tin orbitals method in combination with the coherent potential approximation, we calculate the γ surface for the disordered Cu-Al, Cu-Zn, Cu-Ga, Cu-Ni, Pd-Ag and Pd-Au alloys. Studying the effect of segregation of the solute to the stacking fault planes shows that only the local chemical composition affects the γ surface. The calculated alloying trends are discussed using the electronic band structure of the base and distorted alloys.Based on our γ surface results, we demonstrate that the previous revealed 'universal scaling law' between the intrinsic energy barriers (IEBs) is well obeyed in random solid solutions. This greatly simplifies the calculations of the twinning measure parameters or the critical twinning stress. Adopting two twinnability measure parameters derived from the IEBs, we find that in binary Cu alloys, Al, Zn and Ga increase the twinnability, while Ni decreases it. Aluminum and gallium yield similar effects on the twinnability. PMID:24903220

  17. Galvanic corrosion behavior of titanium implants coupled to dental alloys.

    PubMed

    Cortada, M; Giner, L; Costa, S; Gil, F J; Rodríguez, D; Planell, J A

    2000-05-01

    The corrosion of five materials for implant suprastructures (cast-titanium, machined-titanium, gold alloy, silver-palladium alloy and chromium-nickel alloy), was investigated in vitro, the materials being galvanically coupled to a titanium implant. Various electrochemical parameters E(CORR), i(CORR) Evans diagrams, polarization resistance and Tafel slopes) were analyzed. The microstructure of the different dental materials was observed before and after corrosion processes by optical and electron microscopy. Besides, the metallic ions released in the saliva environment were quantified during the corrosion process by means of inductively coupled plasma-mass spectrometry technique (ICP-MS). The cast and machined titanium had the most passive current density at a given potential and chromium-nickel alloy had the most active critical current density values. The high gold content alloys have excellent resistance corrosion, although this decreases when the gold content is lower in the alloy. The palladium alloy had a low critical current density due to the presence of gallium in this composition but a selective dissolution of copper-rich phases was observed through energy dispersive X-ray analysis. PMID:15348025

  18. ZIRCONIUM ALLOY

    DOEpatents

    Wilhelm, H.A.; Ames, D.P.

    1959-02-01

    A binary zirconiuin--antimony alloy is presented which is corrosion resistant and hard containing from 0.07% to 1.6% by weight of Sb. The alloys have good corrosion resistance and are useful in building equipment for the chemical industry.

  19. URANIUM ALLOYS

    DOEpatents

    Seybolt, A.U.

    1958-04-15

    Uranium alloys containing from 0.1 to 10% by weight, but preferably at least 5%, of either zirconium, niobium, or molybdenum exhibit highly desirable nuclear and structural properties which may be improved by heating the alloy to about 900 d C for an extended period of time and then rapidly quenching it.

  20. Nonswelling alloy

    DOEpatents

    Harkness, S.D.

    1975-12-23

    An aluminum alloy containing one weight percent copper has been found to be resistant to void formation and thus is useful in all nuclear applications which currently use aluminum or other aluminum alloys in reactor positions which are subjected to high neutron doses.

  1. POLLUTION PREVENTION IN THE SEMICONDUCTOR INDUSTRY THROUGH RECOVERY AND RECYCLING OF GALLIUM AND ARSENIC FROM GAAS POLISHING WASTES

    EPA Science Inventory

    A process was developed for the recovery of both arsenic and gallium from gallium arsenide polishing wastes. The economics associated with the current disposal techniques utilizing ferric hydroxide precipitation dictate that sequential recovery of toxic arsenic and valuble galliu...

  2. Bone tissue incorporates in vitro gallium with a local structure similar to gallium-doped brushite.

    PubMed

    Korbas, M; Rokita, E; Meyer-Klaucke, W; Ryczek, J

    2004-01-01

    During mineral growth in rat bone-marrow stromal cell cultures, gallium follows calcium pathways. The dominant phase of the cell culture mineral constitutes the poorly crystalline hydroxyapatite (HAP). This model system mimics bone mineralization in vivo. The structural characterization of the Ga environment was performed by X-ray absorption spectroscopy at the Ga K-edge. These data were compared with Ga-doped synthetic compounds (poorly crystalline hydroxyapatite, amorphous calcium phosphate and brushite) and with strontium-treated bone tissue, obtained from the same culture model. It was found that Sr(2+) substitutes for Ca(2+) in the HAP crystal lattice. In contrast, the replacement by Ga(3+) yielded a much more disordered local environment of the probe atom in all investigated cell culture samples. The coordination of Ga ions in the cell culture minerals was similar to that of Ga(3+), substituted for Ca(2+), in the Ga-doped synthetic brushite (Ga-DCPD). The Ga atoms in the Ga-DCPD were coordinated by four oxygen atoms (1.90 A) of the four phosphate groups and two oxygen atoms at 2.02 A. Interestingly, the local environment of Ga in the cell culture minerals was not dependent on the onset of Ga treatment, the Ga concentration in the medium or the age of the mineral. Thus, it was concluded that Ga ions were incorporated into the precursor phase to the HAP mineral. Substitution for Ca(2+ )with Ga(3+) distorted locally this brushite-like environment, which prevented the transformation of the initially deposited phase into the poorly crystalline HAP. PMID:14648284

  3. Properties of Closed-Shell Titanium Silicate and Gallium-Containing Semiconductor Systems

    NASA Astrophysics Data System (ADS)

    Stoute, Nicholas Aaron

    We demonstrate that an atomic-scale approach may be appropriate for the analysis of the compositional and bonding properties of titanium silicate alloys and shallow d-core level reflectance spectra of gallium-compound semiconductors. Ti silicate analysis was conducted using X-Ray Absorption Spectroscopy (XAS), X-Ray Photoemission Spectroscopy (XPS), and Spectroscopic Ellipsometry (SE) data taken on a range of Ti-silicate alloys. XAS data were obtained by the Lucovsky group at Stanford Synchrotron Radiation Laboratories (SSRL) at the Stanford Linear Accelerator Center (SLAC), and were used as the primary source of information. To bolster conclusions we solicited XPS data from the Opila Laboratory at the University of Delaware, which were provided by Les Fleming. We also took SE data on Ti silicate alloys annealed at different temperatures using two ellipsometers, one of which was built by the author specifically to probe energies in the vacuum uv range. Reflectance data from 20 to 25 eV, which contain spectral features due to transitions from Ga3d core levels, were obtained on GaP, GaAs, GaSb, GaSe, and GaPxAs1ƒ{x at the storage ring Tantalus 1 at the Stoughton Synchrotron Radiation Center by Aspnes and co-workers from about 1980 to 1982. Ti L2,3 XAS data were fitted with reference spectra to obtain 4-fold coordination concentrations (in differing symmetries) and 6-fold coordination concentrations with respect to alloy composition and annealing. Analyzing the concentrations allowed us to draw conclusions on coordination with respect to alloy composition and annealing. We were able to model the 4-fold ¡§in solution¡¨ to 6-fold phase-segregated conversion as a stochastic process, and we found a complete conversion to 6-fold phase-segregated TiO 2 through annealing with at least 36% Ti and above. We attributed this phase segregation to a striation effect previously reported in the literature. XAS OK1 spectra corroborate these results. Investigation of the XPS Ti L 2,3 data verified the formal Ti valence in the Ti silicate alloys as +4. Through atomic-multiplet calculations, we show that because of Coulombic and spin orbit effects the final states of the Ti L2,3 spectra do not maintain any significant degeneracy, even in the absence of a crystal field. Dielectric functions from 1.5 to 9.0 eV, extracted from the SE data obtained on annealed Ti silicate alloys, verified that significant coordination change occurred between the annealing temperature of 500 and 700 °C. A local atomic multiplet theory was applied to investigate the Ga3d shallow core-level spectra of GaP, GaAs, GaSb, GaSe, and GaAs1-xP x. This is a novel application of an existing theory that is typically used for higher-energy transitions. We modeled these spectra quantitatively as a Ga+3 closed-shell ion affected by perturbations on 3d hole-4p electron final states, specifically spin-orbit effects on the hole and electron, and a crystal-field effect on the hole. The crystal-field perturbation arises from the surrounding bond charges and positive ligand anions. Radial-strength parameters were obtained through a least-squares process, and general trends identified with respect to anion electronegativity. Primary conclusion drawn is that the crystal-field effect, in addition to the spin-orbit interaction, plays a significant role in breaking d-level degeneracy, and consequently is necessary to understand shallow 3d core level spectra.

  4. Coherent near infrared photodetection with indium gallium arsenide based optoelectronic devices

    NASA Astrophysics Data System (ADS)

    Fu, Jun-Xian

    Over the extremely broad electromagnetic spectrum, the near-infrared region (0.7--3 mum) is of great interests to physicists, chemists and biologists. Coherent photo-detection in the near-infrared as well as visible and other wavelength regions is extremely useful in identifying coherent light sources from the noisy background. It has great potential to be applied to single-molecule detection by surface-enhanced coherent anti-Stokes Raman scattering. Other applications include chemical gas detection, remote sensing and environmental monitoring, semiconductor processing control and others. Indium gallium arsenide (InGaAs) based optoelectronic devices have been extensively investigated in the wavelength range extending from 800nm for gallium-rich material to 3mum for indium-rich material. A range of InGaAs alloys with bandgap energies in the near infrared wavelength range are investigated by solid-source molecular beam epitaxy (SSMBE). They include strain-free standard In0.532Ga0.468As and In0.532Ga0.468 AsNxSby lattice-matched to InP substrates, highly strained pseudomorphic InxGa1-xAs/InyGa 1-yAs quantum structures on InP substrates and relaxed metamorphic thick Inx>0.8Ga1-xAs device layers with cyclic arsenic-assisted in-situ annealed step-graded InAlAs buffer layers on GaAs and InP substrates. An InP/InAlAs/InGaAs heterojunction bipolar phototransistor (HPT) is designed, simulated and fabricated. The electrical and optical properties, such as responsivity and spectral response, of the HPT are characterized. A compact standing-wave Fourier-transform interferometer system capable of coherent detection in the near-infrared region is demonstrated. A new technique of identifying coherent light sources using harmonic Fourier spectra analysis is developed. The system only includes a PZT-controlled gold-coated scan mirror and a partial-transparent (3.8% single-path loss) InP/InAlAs/InGaAs HPT. The close-loop scan range of PZT-controlled mirror is 32mum. With such mirror scan length, at the harmonic 5th order spectrum components, the resolution of the demonstrated interferometer is 37.5cm-1 with the free spectral range ˜340nm and central spectral position at 1500nm. The system resolution could reach 1 cm-1 with improved system design and elements selection.

  5. The development and implementation of industrial hydrometallurgical gallium recovery of the Clarksville Refinery waste residue

    NASA Astrophysics Data System (ADS)

    Fayram, Todd S.

    Todd Fayram, the Gordonsville Operation of Pasminco US Inc., and the Center for Advanced Mineral and Metallurgical Processing (CAMP) at Montana Tech studied, developed and implemented a pilot scale hydrometallurgical facility for the industrial recovery of gallium. This thesis describes the testing and engineering program that culminated in this successful recovery of gallium through process described herein.

  6. Low temperature recombination and trapping analysis in high purity gallium arsenide by microwave photodielectric techniques

    NASA Technical Reports Server (NTRS)

    Khambaty, M. B.; Hartwig, W. H.

    1972-01-01

    Some physical theories pertinent to the measurement properties of gallium arsenide are presented and experimental data are analyzed. A model for explaining recombination and trapping high purity gallium arsenide, valid below 77 K is assembled from points made at various places and an appraisal is given of photodielectric techniques for material property studies.

  7. Synthesis and use of (polyfluoroaryl)fluoroanions of aluminum, gallium and indium

    DOEpatents

    Marks, Tobin J.; Chen, You-Xian

    2000-01-01

    Salts of (polyfluoroaryl)fluoroanions of aluminum, gallium, and indium are described. The (polyfluoroaryl)fluoroanions have the formula [ER'R"R'"F].sup..crclbar. wherein E is aluminum, gallium, or indium, wherein F is fluorine, and wherein R', R", and R'" is each a fluorinated phenyl, fluorinated biphenyl, or fluorinated polycyclic group.

  8. Unexpected gallium uptake in benign pulmonary pathology. Report of two cases

    SciTech Connect

    McLean, R.G.; Choy, D.; Murray, I.P.

    1984-12-01

    Two cases in which pulmonary gallium uptake was demonstrated in benign conditions are reported. In one, the abnormality permitted localization of a benign mesothelioma, while in the other patient it was associated with pulmonary fibrosis resulting from therapeutic irradiation. These cases extend the causes of gallium accumulation in which neither malignancy nor infection is responsible.

  9. Failure of Gallium-67 scintigraphy to identify reliably noninfectious interstitial nephritis: concise communication

    SciTech Connect

    Graham, G.D.; Lundy, M.M.; Moreno, A.J.

    1983-07-01

    Gallium-67 scintigraphy has been reported to be useful in the diagnosis of noninfectious interstitial nephritis. We studied 12 patients with Ga-67 citrate that were diagnosed as having noninfectious interstitial nephritis on renal biopsy. Only seven of the twelve patients with interstitial nephritis on biopsy were scan-positive. Gallium-67 scintigraphy may not reliably identify noninfectious interstitial nephritis.

  10. Aluminum alloy

    NASA Technical Reports Server (NTRS)

    Blackburn, Linda B. (Inventor); Starke, Edgar A., Jr. (Inventor)

    1989-01-01

    This invention relates to aluminum alloys, particularly to aluminum-copper-lithium alloys containing at least about 0.1 percent by weight of indium as an essential component, which are suitable for applications in aircraft and aerospace vehicles. At least about 0.1 percent by weight of indium is added as an essential component to an alloy which precipitates a T1 phase (Al2CuLi). This addition enhances the nucleation of the precipitate T1 phase, producing a microstructure which provides excellent strength as indicated by Rockwell hardness values and confirmed by standard tensile tests.

  11. PLUTONIUM ALLOYS

    DOEpatents

    Chynoweth, W.

    1959-06-16

    The preparation of low-melting-point plutonium alloys is described. In a MgO crucible Pu is placed on top of the lighter alloying metal (Fe, Co, or Ni) and the temperature raised to 1000 or 1200 deg C. Upon cooling, the alloy slug is broke out of the crucible. With 14 at. % Ni the m.p. is 465 deg C; with 9.5 at. % Fe the m.p. is 410 deg C; and with 12.0 at. % Co the m.p. is 405 deg C. (T.R.H.) l6262 l6263 ((((((((Abstract unscannable))))))))

  12. Investigation of the variations in the crystallization front shape during growth of gadolinium gallium and terbium gallium crystals by the Czochralski method

    SciTech Connect

    Budenkova, O. N. Vasiliev, M. G.; Yuferev, V. S.; Ivanov, I. A.; Bul'kanov, A. M.; Kalaev, V. V.

    2008-12-15

    Numerical investigation of the variations in the crystallization front shape during growth of gadolinium gallium and terbium gallium garnet crystals in the same thermal zone and comparison of the obtained results with the experimental data have been performed. It is shown that the difference in the behavior of the crystallization front during growth of the crystals is related to their different transparency in the IR region. In gadolinium gallium garnet crystals, which are transparent to thermal radiation, a crystallization front, strongly convex toward the melt, is formed in the growth stage, which extremely rapidly melts under forced convection. Numerical analysis of this process has been performed within the quasistationary and nonstationary models. At the same time, in terbium gallium garnet crystals, which are characterized by strong absorption of thermal radiation, the phase boundary shape changes fairly smoothly and with a small amplitude. In this case, as the crystal is pulled, the crystallization front tends to become convex toward the crystal bulk.

  13. Critical evaluation of the gallium-67 scan for surgical patients with lung cancer

    SciTech Connect

    McKenna, R.J. Jr.; Haynie, T.P.; Libshitz, H.I.; Mountain, C.F.; McMurtrey, M.J.

    1985-04-01

    Seventy-five patients with lung cancer underwent a gallium scan and thoracotomy with total mediastinal nodal dissection. Evaluation of mediastinal lymph nodes by means of the gallium scan showed a sensitivity of 23 percent (3/13), a specificity of 82 percent (31/38), an accuracy of 67 percent (34/51), a positive predictive valve of 30 percent (3/10), and a negative predictive value of 76 percent (31/41) in those patients whose primary tumors demonstrated uptake of radioactive gallium. The low sensitivity was due to an inability to detect microscopic disease in mediastinal lymph nodes. The specificity was decreased by gallium-67 uptake in enlarged inflamed nodes that contained no metastases. These results do not support the use of the gallium scan in the selection of patients with lung cancer for thoracotomy.

  14. The Inhibition of Escherichia coli Biofilm Formation by Gallium Nitrate-Modified Titanium.

    PubMed

    Zhu, Yuanyuan; Qiu, Yan; Chen, Ruiqi; Liao, Lianming

    2015-08-01

    Periprosthetic infections are notoriously difficult to treat due to biofilm formation. Previously, we reported that gallium-EDTA attached to PVC (polyvinyl chloride) surface could prevent bacterial colonization. Herein we examined the effect of this gallium-EDTA complex on Escherichia coli biofilm formation on titanium. It was clearly demonstrated that gallium nitrate significantly inhibited the growth and auto-aggregation of Escherichia coli. Furthermore, titanium with gallium-EDTA coating resisted bacterial colonization as indicated by crystal violet staining. When the chips were immersed in human serum and incubated at 37 °C, they demonstrated significant antimicrobial activity after more than 28 days of incubation. These findings indicate that gallium-EDTA coating of implants can result in a surface that can resist bacterial colonization. This technology holds great promise for the prevention and treatment of periprosthetic infections. PMID:26369125

  15. Potential use of gallium-doped phosphate-based glass material for periodontitis treatment.

    PubMed

    Sahdev, Rohan; Ansari, Tahera I; Higham, Susan M; Valappil, Sabeel P

    2015-07-01

    This study aimed at evaluating the potential effect of gallium-incorporated phosphate-based glasses towards periodontitis-associated bacteria, Porphyromonas gingivalis, and matrix metalloproteinase-13. Periodontitis describes a group of inflammatory diseases of the gingiva and supporting structures of the periodontium. They are initiated by the accumulation of plaque bacteria, such as the putative periodontal pathogen Porphyromonas gingivalis, but the host immune response such as elevated matrix metalloproteinases are the major contributing factor for destruction of periodontal tissues. Antibacterial assays of gallium-incorporated phosphate-based glasses were conducted on Porphyromonas gingivalis ATCC 33277 using disc diffusion assay on fastidious anaerobe agar and liquid broth assay in a modified tryptic soy broth. In vitro study investigated the effect of gallium on purified recombinant human matrix metalloproteinase-13 activity using matrix metalloproteinase assay kit. In vivo biocompatibility of gallium-incorporated phosphate-based glass was evaluated in rats as subcutaneous implants. Antibacterial assay of gallium displayed activity against Porphyromonas gingivalis (inhibition zone of 22??0.5?mm compared with 0?mm for control glass, c-PBG). Gallium in the glass contributed to growth inhibitory effect on Porphyromonas gingivalis (up to 1.30 reductions in log?10 values of the viable counts compared with control) in a modified tryptic soy broth. In vitro study showed gallium-incorporated phosphate-based glasses inhibited matrix metalloproteinase activity significantly (p???0.01) compared with c-PBG. Evaluation of in vivo biocompatibility of gallium-incorporated phosphate-based glasses in rats showed a non-toxic and foreign body response after 2 weeks of implantation. The results indicate that gallium ions might act on multiple targets of biological mechanisms underlying periodontal disease. Moreover, gallium-incorporated phosphate-based glasses are biocompatible in a rat model. The findings warrant further investigation and will have important clinical implications in the future treatment and management of periodontitis. PMID:25681404

  16. COATED ALLOYS

    DOEpatents

    Harman, C.G.; O'Bannon, L.S.

    1958-07-15

    A coating is described for iron group metals and alloys, that is particularly suitable for use with nickel containing alloys. The coating is glassy in nature and consists of a mixture containing an alkali metal oxide, strontium oxide, and silicon oxide. When the glass coated nickel base metal is"fired'' at less than the melting point of the coating, it appears the nlckel diffuses into the vitreous coating, thus providing a closely adherent and protective cladding.

  17. BRAZING ALLOYS

    DOEpatents

    Donnelly, R.G.; Gilliland, R.G.; Slaughter, G.M.

    1962-02-20

    A brazing alloy is described which, in the molten state, is characterized by excellent wettability and flowability and is capable of forming a corrosion-resistant brazed joint. At least one component of said joint is graphite and the other component is a corrosion-resistant refractory metal. The brazing alloy consists essentially of 40 to 90 wt % of gold, 5 to 35 wt% of nickel, and 1 to 45 wt% of tantalum. (AEC)

  18. Gallium-68 chemistry for labeling platelets, proteins and lipoproteins

    SciTech Connect

    Yano, Y.; Budinger, T.F.; Ebbe, S.N.; Mathis, C.A.; Moore, D.H.; Singh, M.; Brennan, K.; Moyer, B.R.; Nichols, A.

    1984-07-01

    Generator produced gallium-68 is a convenient useful radionuclide for positron emission tomography (PET) investigations. Gallium-68 labeled platelets and low density lipoproteins would be useful agents for PET studies of thrombosis and atherosclerosis in cardiovascular disease. To label these agents with Ga-68, we have studied the effects of trace metal contaminants in 1 N HCl elutions of Ga-68 from germanium-68 absorbed on a stannic oxide column. Studies were conducted on the formation and characteristics of Ga-68 complexes with the ligands 8-hydroxyquinoline, tropolone, and mercaptopyridine-N-oxide (MPO). Various parameters such as pH, buffers, concentration of ligand, and incubation or stability with time were investigated. High performance liquid chromatography and instant thin layer chromatography were used to analyze the Ga-68 ligand preparations. Platelets separated from human, dog, and rabbit plasma were incubated with the Ga-68 complexes and the labeling yields and in vivo survival were determined. The accumulation of the platelets in the ballon catheter scraped aorta of the rabbit was determined by PET imaging studies, tissue counting in a gamma well counter, and en-face autoradiography of the arterial wall. The Ga-68 complexes of MPO gave 40 to 60% labeling efficiency of rabbit platelets which accumulated about fourfold more in the damaged aorta compared to the normal. Gallium-68 was attached to low density lipoproteins (LDL) with the bifunctional chelate of DTPA. Low pressure gel column chromatography and HPLC were used to preparatively separate and analyze the Ga-68 LDL for uptake studies in the healing endothelium of the scraped aorta rabbit model. The Ga-68 LDL labeling yield was 80 to 85% with a radiochemical purity 90 to 95%. 22 references, 10 figures, 4 tables.

  19. Modified silicon-germanium alloys with improved performance. [thermoelectric material

    NASA Technical Reports Server (NTRS)

    Pisharody, R. K.; Garvey, L. P.

    1978-01-01

    This paper discusses the results of a program on the modification of silicon-germanium alloys by means of small extraneous material additions in order to improve their figures-of-merit. A review of the properties that constitute the figure-of-merit indicates that it is the relatively high thermal conductivity of silicon-germanium alloys that is responsible for their low values of figure-of-merit. The intent of the effort discussed in this paper is therefore the reduction of the thermal conductivity of silicon-germanium alloys by minor alloy additions and/or changes in the basic structure of the material. Because Group III and V elements are compatible with silicon and germanium, the present effort in modifying silicon-germanium alloys has concentrated on additions of gallium phosphide. A significant reduction in thermal conductivity, approximately 40 to 50 percent, has been demonstrated while the electrical properties are only slightly affected as a result. The figure-of-merit of the resultant material is enhanced over that of silicon-germanium alloys and when fully optimized is potentially better than that of any other presently available thermoelectric material.

  20. Gallium uptake in tryptophan-related pulmonary disease

    SciTech Connect

    Kim, S.M.; Park, C.H.; Intenzo, C.M.; Patel, R. )

    1991-02-01

    We describe a patient who developed fever, fatigue, muscle weakness, dyspnea, skin rash, and eosinophilia after taking high doses of tryptophan for insomnia for two years. A gallium-67 scan revealed diffuse increased uptake in the lung and no abnormal uptake in the muscular distribution. Bronchoscopy and biopsy confirmed inflammatory reactions with infiltration by eosinophils, mast cells, and lymphocytes. CT scan showed an interstitial alveolar pattern without fibrosis. EMG demonstrated diffuse myopathy. Muscle biopsy from the right thigh showed an inflammatory myositis with eosinophilic and lymphocytic infiltrations.

  1. Testing of gallium arsenide solar cells on the CRRES vehicle

    NASA Technical Reports Server (NTRS)

    Trumble, T. M.

    1985-01-01

    A flight experiment was designed to determine the optimum design for gallium arsenide (GaAs) solar cell panels in a radiation environment. Elements of the experiment design include, different coverglass material and thicknesses, welded and soldered interconnects, different solar cell efficiencies, different solar cell types, and measurement of annealing properties. This experiment is scheduled to fly on the Combined Release and Radiation Effects Satellite (CRRES). This satellite will simultaneously measure the radiation environment and provide engineering data on solar cell degradation that can be directly related to radiation damage.

  2. Two gallium antimony sulfides built on a novel heterometallic cluster.

    PubMed

    Feng, Mei-Ling; Xie, Zai-Lai; Huang, Xiao-Ying

    2009-05-01

    Two gallium antimony sulfides, [Ni(en)(3)][Ga(2)Sb(2)S(7)] (1) and [(Me)(2)NH(2)](2)[Ga(2)Sb(2)S(7)] (2), have been prepared under mild solvothermal conditions. Both structures feature a two-dimensional network in which two GaS(4) tetrahedra and two SbS(3) trigonal pyramids are combined to form a heterometallic cluster of {Ga(2)Sb(2)S(9)} as a new secondary building unit. The thermal properties of 1 and 2 have been studied by thernogravimetric analysis, and the optical properties of 1 and 2 have been characterized by UV-vis spectra. PMID:19331385

  3. Visible light metasurfaces based on gallium nitride high contrast gratings

    NASA Astrophysics Data System (ADS)

    Wang, Zhenhai; He, Shumin; Liu, Qifa; Wang, Wei

    2016-05-01

    We propose visible-light metasurfaces (VLMs) capable of serving as lens and beam deflecting element based on gallium nitride (GaN) high contrast gratings (HCGs). By precisely manipulating the wavefront of the transmitted light, we theoretically demonstrate an HCG focusing lens with transmissivity of 86.3%, and a VLM with beam deflection angle of 6.09° and transmissivity as high as 91.4%. The proposed all-dielectric metasurfaces are promising for GaN-based visible light-emitting diodes (LEDs), which would be robust and versatile for controlling the output light propagation and polarization, as well as enhancing the extraction efficiency of the LEDs.

  4. Electronic structure and properties of layered gallium telluride

    NASA Astrophysics Data System (ADS)

    Shenoy, U. Sandhya; Gupta, Uttam; Narang, Deepa S.; Late, Dattatray J.; Waghmare, Umesh V.; Rao, C. N. R.

    2016-05-01

    Layer-dependent electronic structure and properties of gallium monochalcogenides, GaX where X = S, Se, Te, have been investigated using first-principles calculations based on various functionals, with a motivation to assess their use in photocatalytic water splitting. Since hydrogen evolution by water splitting using visible light provides a promising way for solar energy conversion, both theoretical and experimental studies have been carried out on the photochemical hydrogen evolution by GaTe. We also present the Raman spectra of GaTe examined by both theory and experiment.

  5. Improved performance design of gallium arsenide solar cells for space

    NASA Technical Reports Server (NTRS)

    Parekh, R. H.; Barnett, A. M.

    1984-01-01

    An improved design, shallow junction heteroface, n-p, gallium arsenide solar cell for space applications is reported, with a predicted AM0 efficiency in the 21.9 to 23.0 percent range. The optimized n-p structure, while slightly more efficient, has the added advantage of being less susceptible to radiation-induced degradation by virtue of this thin top junction layer. Detailed spectral response curves and an analysis of the loss mechanisms are reported. The details of the design are readily measurable. The optimized designs were reached by quantifying the dominant loss mechanisms and then minimizing them by using computer simulations.

  6. Spectroscopy of vanadium (III) doped gallium lanthanum sulphide chalcogenide glass

    NASA Astrophysics Data System (ADS)

    Hughes, M.; Rutt, H.; Hewak, D.; Curry, R. J.

    2007-01-01

    Vanadium doped gallium lanthanum sulphide glass (V:GLS) displays three absorption bands at 580, 730, and 1155nm identified by photoluminescence excitation measurements. Broad photoluminescence, with a full width at half maximum of ˜500nm, is observed peaking at 1500nm when exciting at 514, 808, and 1064nm. The fluorescence lifetime and quantum efficiency at 300K were measured to be 33.4μs and 4%, respectively. From the available spectroscopic data, the authors propose the vanadium ions' valence to be 3+ and be in tetrahedral coordination. The results indicate a potential for the development of a laser or optical amplifier based on V:GLS.

  7. Interdiffusion of magnesium and iron dopants in gallium nitride

    NASA Astrophysics Data System (ADS)

    Tsuchiya, Tomonobu; Kitatani, Takeshi; Terano, Akihisa; Mochizuki, Kazuhiro

    2015-03-01

    The interdiffusion of magnesium and iron in gallium nitride (GaN), i.e., magnesium-iron interdiffusion, was investigated using magnesium-doped GaN layers on iron-doped GaN substrates. The investigation confirms that the magnesium-iron interdiffusion strongly depends on the concentrations of magnesium and iron, that is, it occurs when the iron and magnesium concentrations are high (magnesium: 2 × 1020 cm-3 iron: 2 × 1019 cm-3). It also confirms that diffused iron in the magnesium-doped GaN layer acts as a nonradiative recombination center in GaN.

  8. Tomographic gallium-67 citrate scanning: useful new surveillance for metastatic melanoma

    SciTech Connect

    Kirkwood, J.M.; Myers, J.E.; Vlock, D.R.; Neumann, R.; Ariyan, S.; Gottschalk, A.; Hoffer, P.

    1982-11-01

    Conventional gallium scans are not useful to evaluate patients with metastatic melanoma. We evaluated a new method of tomographic gallium imaging. One hundred fourteen tomographic scans were obtained in a prospective surveillance study of 67 patients over a 3-year period. Scans were evaluated and compared to findings of independent clinical evaluations. Sensitivity of gallium identification of tumor involving peripheral lymph nodes and soft tissues, abdomen, mediastinum, and osseous sites was 68% to 100%; overall sensitivity of this technique is 82% with specificity of 99% in 570 organ system assessments. Analysis of discordant findings when a site was clinically occult but gallium-positive showed gallium uptake to be true-positive in six of seven lymphatic sites, three of three lung and mediastinal sites, six of six abdominal sites, but in no brain or bone sites. Gallium lesions identified by computed tomographic scans proved to be false-positive at one lymphatic and one bone site, and false-negative at four otherwise clinically evident lymph node and soft tissue sites, seven pulmonary sites, and four brain sites. Gallium tomographic scanning provides a composite assessment of melanoma and may eliminate the need for other studies.

  9. Tomographic gallium-67 citrate scanning. Useful new surveillance for metastatic melanoma

    SciTech Connect

    Kirkwood, J.M.; Myers, J.E.; Vlock, D.R.; Neumann, R.; Ariyan, S.; Gottschalk, A.; Hoffer, P.

    1983-07-01

    Conventional gallium scans are not useful to evaluate patients with metastatic melanoma. We evaluated a new method of tomographic gallium imaging. One hundred fourteen tomographic scans were obtained in a prospective surveillance study of 67 patients over a 3-year period. Scans were evaluated and compared to findings of independent clinical evaluations. Sensitivity of gallium identification of tumor involving peripheral lymph nodes and soft tissues, abdomen, mediastinum, and osseous sites was 68% to 100%; overall sensitivity of this technique is 82% with specificity of 99% in 570 organ system assessments. Analysis of discordant findings when a site was clinically occult but gallium-positive showed gallium uptake to be true-positive in six of seven lymphatic sites, three of three lung and mediastinal sites, six of six abdominal sites, but in no brain or bone sites. Gallium lesions identified by computed tomographic scans proved to be false-positive at one lymphatic and one bone site, and false-negative at four otherwise clinically evident lymph node and soft tissue sites, seven pulmonary sites, and four brain sites. Gallium tomographic scanning provides a composite assessment of melanoma and may eliminate the need for other studies.

  10. Study on natural convection capability of liquid gallium for passive decay heat removal system (PDHRS)

    SciTech Connect

    Kang, S.; Ha, K. S.; Lee, S. W.; Park, S. D.; Kim, S. M.; Seo, H.; Kim, J. H.; Bang, I. C.

    2012-07-01

    The safety issues of the SFRs are important due to the fact that it uses sodium as a nuclear coolant, reacting vigorously with water and air. For that reason, there are efforts to seek for alternative candidates of liquid metal coolants having excellent heat transfer property and to adopt improved safety features to the SFR concepts. This study considers gallium as alternative liquid metal coolant applicable to safety features in terms of chemical activity issue of the sodium and aims to experimentally investigate the natural convection capability of gallium as a feasibility study for the development of gallium-based passive safety features in SFRs. In this paper, the design and construction of the liquid gallium natural convection loop were carried out. The experimental results of heat transfer coefficient of liquid gallium resulting in heat removal {approx}2.53 kW were compared with existing correlations and they were much lower than the correlations. To comparison of the experimental data with computer code analysis, gallium property code was developed for employing MARS-LMR (Korea version of RELAP) based on liquid gallium as working fluid. (authors)

  11. Technetium-99m DTPA aerosol and gallium scanning in acquired immune deficiency syndrome

    SciTech Connect

    Picard, C.; Meignan, M.; Rosso, J.; Cinotti, L.; Mayaud, C.; Revuz, J.

    1987-07-01

    In 11 non-smoking AIDS patients suspected of pneumocystis carinii pneumonia (PCP), the results of Tc-99m DTPA aerosol clearances, gallium scans, and arterial blood gases were compared with those of bronchoalveolar lavage (BAL). Nine patients had PCP. All had increased clearances five times higher than the normal (5.6 +/- 2.3% X min-1 vs 1.1 +/- 0.34% X min-1, N = 10, P less than 0.001), suggesting an increased alveolar permeability. Gallium scans were abnormal in six patients but normal or slightly abnormal in the three others. Four of these nine patients had normal chest x-rays. In two of these the gallium scan was abnormal, but in the two others, only the increased Tc-99m DTPA clearances showed evidence of lung disease. Two patients had normal BAL, with normal clearances and gallium scans. Four out of the nine patients with PCP were studied after treatment. Three recovered and had normal clearance and gallium scans. One still had PCP with increased clearance but normal gallium scan. Gallium scanning and Tc-99m DTPA clearance are useful for detecting lung disease in AIDS patients with suspected PCP and for prompting BAL when chest x-rays and PaO/sub 2/ levels are normal. Due to its high sensitivity, a normal Tc-99m DTPA clearance could avoid BAL.

  12. Gallium-67 citrate imaging in underground coal miners

    SciTech Connect

    Kanner, R.E.; Barkman, H.W. Jr.; Rom, W.N.; Taylor, A.T. Jr.

    1985-01-01

    Twenty-two underground coal workers with 27 or more years of coal dust exposure were studied with gallium-67 citrate (Ga-67) imaging. Radiographic evidence of coal workers indicates that pneumoconiosis (CWP) was present in 12 subjects. The Ga-67 scan was abnormal in 11 of 12 with, and 9 of 10 without, CWP. The Ga-67 uptake index was significantly correlated with total dust exposure (p less than 0.01) and approached significant correlation with the radiographic profusion of the nodules (0.10 greater than p greater than 0.05). There was no correlation between Ga-67 uptake and spirometric function, which was normal in this group of patients; furthermore, increased lung uptake of gallium did not indicate a poor prognosis in subjects no longer exposed to coal dust. While coal dust exposure may be associated with positive Ga-67 lung scan in coal miners with many years of coal dust exposure, the scan provided no information not already available from a careful exposure history and a chest radiograph. Since Ga-67 scanning is a relatively expensive procedure the authors would recommend that its use in subjects with asymptomatic CWP be limited to an investigative role and not be made part of a routine evaluation.

  13. Exciton pumping across type-I gallium chalcogenide heterojunctions

    NASA Astrophysics Data System (ADS)

    Cai, Hui; Kang, Jun; Sahin, Hasan; Chen, Bin; Suslu, Aslihan; Wu, Kedi; Peeters, Francois; Meng, Xiuqing; Tongay, Sefaattin

    2016-02-01

    Quasi-two-dimensional gallium chalcogenide heterostructures are created by transferring exfoliated few-layer GaSe onto bulk GaTe sheets. Luminescence spectroscopy measurements reveal that the light emission from underlying GaTe layers drastically increases on heterojunction regions where GaSe layers make contact with the GaTe. Density functional theory (DFT) and band offset calculations show that conduction band minimum (CBM) (valance band maximum (VBM)) values of GaSe are higher (lower) in energy compared to GaTe, forming type-I band alignment at the interface. Consequently, GaSe layers provide photo-excited electrons and holes to GaTe sheets through relatively large built-in potential at the interface, increasing overall exciton population and light emission from GaTe. Observed results are not specific to the GaSe/GaTe system but observed on GaS/GaSe heterolayers with type-I band alignment. Observed experimental findings and theoretical studies provide unique insights into interface effects across dissimilar gallium chalcogenides and offer new ways to boost optical performance by simple epitaxial coating.

  14. Multiscale modelling of gallium induced embrittlement in aluminium

    NASA Astrophysics Data System (ADS)

    Bhogireddy, Venkata Sai Pavan Kumar; Todorova, Mira; Spatschek, Robert; Neugebauer, Jörg

    Liquid metal embrittlement is a degradation phenomenon in which a solid metal undergoes brittle failure when it is stressed while in contact with a liquid metal. The transition from ductile to brittle metal failure manifests itself by rapid crack propagations which reduces the elongation to failure ratio. Combining density functional theory calculations with continuum methods, we study the liquid metal embrittlement of aluminium in contact with gallium. Comparing ab initio calculated energies for a Σ 3 and a Σ 5 Al grain boundary and their corresponding surface energies in the presence and absence of Ga, we identify critical Ga concentrations which result in a weakening of the mechanical strength of aluminium. Parametrising the DFT results in continuum model we obtain the concentration as a function of the strain in the system. In a final step we extend this approach and compute the stress field induced by cracks in bulk and at grain boundaries. The stress field explains the large segregation of gallium atoms at the crack tip and the crack tip's subsequent propagation.

  15. [Determination of traces of gallium in air by oscillographic polarography].

    PubMed

    Sun, C; Yang, Z; Cheng, D; Yi, Z; Shen, T; Liu, Z; Bai, Y

    1990-03-01

    Gallium and its compounds in air collected by millipore filter membrane are leached by 10% HNO3 at room temperature. After being adjusted with ammonia solution to pH8-9, the leachate is filtered and the filtrate is evaporated to dryness on a water bath. The residue is dissolved with 2 ml of 10% HNO3 and then into the solution are added 0.5 ml of 5% hydroxylamine hydrochloride solution, 0.20 ml of 5% sulfosalicyclic acid solution, 0.5 ml of NaF solution (1mg F/ml) and 1 drop of methyl red solution. Let it stand for 5 min after the color of the solution turns orange by addition of 1:1 NH4OH solution. Add 0.20ml of 0.20% cupferron solution, 0.20ml of 0.5% diphenyl-guanidine solution (prepared in 95% ethanol) and 0.5ml of acetic acid-ammonium acetate buffer (pH 7.0). Then add water to make the final volume of the test solution to be 10ml and measure the height of the second derivative polarographic wave at -1.08V (vs.SCE). The sensitivity of the method is 0.005-0.10 microgram/ml, the coefficient of variation 6.8%, recovery 97.8%. Within 0.005-0.10 microgram/ml, the wave height is linear with the concentration of gallium. PMID:2365333

  16. Low temperature solid-state synthesis of nanocrystalline gallium nitride

    SciTech Connect

    Wang, Liangbiao; Shi, Liang; Li, Qianwen; Si, Lulu; Zhu, Yongchun; Qian, Yitai

    2012-11-15

    Graphical abstract: Display Omitted Highlights: ► GaN nanocrystalline was prepared via a solid-state reacion at relatively low temperature. ► The sizes and crystallinities of the GaN samples obtained at the different temperatures are investigated. ► The GaN sample has oxidation resistance and good thermal stability below 1000 °C. -- Abstract: Nanocrystalline gallium nitride was synthesized by a solid-state reaction of metallic magnesium powder, gallium sesquioxide and sodium amide in a stainless steel autoclave at a relatively low temperature (400–550 °C). The structures and morphologies of the obtained products were derived from X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). XRD patterns indicated that the products were hexagonal GaN (JCPDS card no. 76-0703). The influence of reaction temperature on size of the products was studied by XRD and TEM. Furthermore, the thermal stability and oxidation resistance of the nanocrystalline GaN were also investigated. It had good thermal stability and oxidation resistance below 800 °C in air.

  17. Exciton pumping across type-I gallium chalcogenide heterojunctions.

    PubMed

    Cai, Hui; Kang, Jun; Sahin, Hasan; Chen, Bin; Suslu, Aslihan; Wu, Kedi; Peeters, Francois; Meng, Xiuqing; Tongay, Sefaattin

    2016-02-12

    Quasi-two-dimensional gallium chalcogenide heterostructures are created by transferring exfoliated few-layer GaSe onto bulk GaTe sheets. Luminescence spectroscopy measurements reveal that the light emission from underlying GaTe layers drastically increases on heterojunction regions where GaSe layers make contact with the GaTe. Density functional theory (DFT) and band offset calculations show that conduction band minimum (CBM) (valance band maximum (VBM)) values of GaSe are higher (lower) in energy compared to GaTe, forming type-I band alignment at the interface. Consequently, GaSe layers provide photo-excited electrons and holes to GaTe sheets through relatively large built-in potential at the interface, increasing overall exciton population and light emission from GaTe. Observed results are not specific to the GaSe/GaTe system but observed on GaS/GaSe heterolayers with type-I band alignment. Observed experimental findings and theoretical studies provide unique insights into interface effects across dissimilar gallium chalcogenides and offer new ways to boost optical performance by simple epitaxial coating. PMID:26759069

  18. High-surface Thermally Stable Mesoporous Gallium Phosphates Constituted by Nanoparticles as Primary Building Blocks

    SciTech Connect

    V Parvulescu; V Parvulescu; D Ciuparu; C Hardacre; H Garcia

    2011-12-31

    In constant, search for micro/mesoporous materials, gallium phosphates, have attracted continued interest due to the large pore size reported for some of these solids in comparison with analogous aluminum phosphates. However up to now, the porosity of gallium phosphates collapsed upon template removal or exposure to the ambient moisture. In the present work, we describe high-surface thermally stable mesoporous gallium phosphates synthesized from gallium propoxide and PCl{sub 3} and different templating agents such as amines (dipropylamine, piperidine and aminopiperidine) and quaternary ammonium salts (C{sub 16}H{sub 33}(CH{sub 3})3NBr and C{sub 16}PyCl). These highly reactive precursors have so far not been used as gallium and phosphate sources for the synthesis of gallophosphates. Conceptually, our present synthetic procedure is based on the fast formation of gallium phosphate nanoparticles via the reaction of gallium propoxide with PCl{sub 3} and subsequent construction of the porous material with nanoparticles as building blocks. The organization of the gallophosphate nanoparticles in stable porous structures is effected by the templates. Different experimental procedures varying the molar composition of the sol-gel, pH and the pretreatment of gallium precursor were assayed, most of them leading to satisfactory materials in terms of thermal stability and porosity. In this way, a series of gallium phosphates with surface are above 200 m{sup 2} g{sup -1}, and narrow pore size from 3 to 6 nm and remarkable thermal stability (up to 550 C) have been prepared. In some cases, the structure tends to show some periodicity and regularity as determined by XRD. The remarkable stability has allowed us to test the catalytic activity of gallophosphates for the aerobic oxidation of alkylaromatics with notable good results. Our report reopens the interest for gallophosphates in heterogeneous catalysis.

  19. Iron-Targeting Antitumor Activity of Gallium Compounds and Novel Insights Into Triapine-Metal Complexes

    PubMed Central

    Antholine, William E.

    2013-01-01

    Abstract Significance: Despite advances made in the treatment of cancer, a significant number of patients succumb to this disease every year. Hence, there is a great need to develop new anticancer agents. Recent Advances: Emerging data show that malignant cells have a greater requirement for iron than normal cells do and that proteins involved in iron import, export, and storage may be altered in cancer cells. Therefore, strategies to perturb these iron-dependent steps in malignant cells hold promise for the treatment of cancer. Recent studies show that gallium compounds and metal-thiosemicarbazone complexes inhibit tumor cell growth by targeting iron homeostasis, including iron-dependent ribonucleotide reductase. Chemical similarities of gallium(III) with iron(III) enable the former to mimic the latter and interpose itself in critical iron-dependent steps in cellular proliferation. Newer gallium compounds have emerged with additional mechanisms of action. In clinical trials, the first-generation-compound gallium nitrate has exhibited activity against bladder cancer and non-Hodgkin's lymphoma, while the thiosemicarbazone Triapine has demonstrated activity against other tumors. Critical Issues: Novel gallium compounds with greater cytotoxicity and a broader spectrum of antineoplastic activity than gallium nitrate should continue to be developed. Future Directions: The antineoplastic activity and toxicity of the existing novel gallium compounds and thiosemicarbazone-metal complexes should be tested in animal tumor models and advanced to Phase I and II clinical trials. Future research should identify biologic markers that predict tumor sensitivity to gallium compounds. This will help direct gallium-based therapy to cancer patients who are most likely to benefit from it. Antioxid. Redox Signal. 00, 000000. PMID:22900955

  20. Electrodeposition of crystalline GaAs on liquid gallium electrodes in aqueous electrolytes.

    PubMed

    Fahrenkrug, Eli; Gu, Junsi; Maldonado, Stephen

    2013-01-01

    Crystalline GaAs (c-GaAs) has been prepared directly through electroreduction of As(2)O(3) dissolved in an alkaline aqueous solution at a liquid gallium (Ga(l)) electrode at modest temperatures (T ≥ 80 °C). Ga(l) pool electrodes yielded consistent electrochemical behavior, affording repetitive measurements that illustrated the interdependences of applied potential, concentration of dissolved As(2)O(3), and electrodeposition temperature on the quality of the resultant c-GaAs(s). Raman spectra indicated the composition of the resultant film was strongly dependent on both the electrodeposition temperature and dissolved concentration of As(2)O(3) but not to the applied bias. For electrodepositions performed either at room temperature or with high (≥0.01 M) concentrations of dissolved As(2)O(3), Raman spectra of the electrodeposited films were consistent with amorphous As(s). X-ray diffractograms of As(s) films collected after thermal annealing indicated metallurgical alloying occurred only at temperatures in excess of 200 °C. Optical images and Raman spectra separately showed the composition of the as-electrodeposited film in dilute (≤0.001 M) solutions of dissolved As(2)O(3)(aq) was pure c-GaAs(s) at much lower temperatures than 200 °C. Diffractograms and transmission electron microscopy performed on as-prepared films confirmed the identity of c-GaAs(s). The collective results thus provide the first clear demonstration of an electrochemical liquid-liquid-solid (ec-LLS) process involving a liquid metal that serves simultaneously as an electrode, a solvent/medium for crystal growth, and a coreactant for the synthesis of a polycrystalline semiconductor. The presented data serve as impetus for the further development of the ec-LLS process as a controllable, simple, and direct route for technologically important optoelectronic materials such as c-GaAs(s). PMID:23265429

  1. Gallium-67 imaging in retroperitoneal fibrosis: Significance of a negative result

    SciTech Connect

    Jacobson, A.F. )

    1991-03-01

    A patient with retroperitoneal fibrosis and right peritracheal and hilar lymphadenopathy was studied using gallium-67-citrate. No abnormal uptake was seen in the regions of retroperitoneal fibrosis, while there was avid uptake in chest lesions later shown to represent small cell lung carcinoma. Retroperitoneal fibrosis which does not show gallium uptake is most likely mature, with few inflammatory elements. In patients with multiple retroperitoneal and/or mediastinal masses, gallium imaging may be useful in identifying the most active sites of disease for possible biopsy and for subsequent monitoring of response to therapy.

  2. Electron transport in zinc-blende wurtzite biphasic gallium nitride nanowires and GaNFETs

    DOE PAGESBeta

    Jacobs, Benjamin W.; Ayres, Virginia M.; Stallcup, Richard E.; Hartman, Alan; Tupta, Mary Ann; Baczewski, Andrew David; Crimp, Martin A.; Halpern, Joshua B.; He, Maoqi; Shaw, Harry C.

    2007-10-19

    Two-point and four-point probe electrical measurements of a biphasic gallium nitride nanowire and current–voltage characteristics of a gallium nitride nanowire based field effect transistor are reported. The biphasic gallium nitride nanowires have a crystalline homostructure consisting of wurtzite and zinc-blende phases that grow simultaneously in the longitudinal direction. There is a sharp transition of one to a few atomic layers between each phase. Here, all measurements showed high current densities. Evidence of single-phase current transport in the biphasic nanowire structure is discussed.

  3. Gallium scintigraphy for diagnosis of septic arthritis and osteomyelitis in children

    SciTech Connect

    Borman, T.R.; Johnson, R.A.; Sherman, F.C.

    1986-05-01

    Thirty-four children with presumptive acute osteomyelitis or septic arthritis underwent early gallium-67 citrate scintigraphy and have been retrospectively reviewed. Diagnostic accuracy using this technique was 91%. Gallium-67 citrate is a more reliable radiopharmaceutical agent for the detection of selected acute musculoskeletal infections than either technetium methylene diphosphonate or indium-111. However, the radiation dosage from gallium is higher than from other radiopharmaceutical agents, and the authors would recommend its use only in cases where the diagnosis cannot be made on the basis of clinical, laboratory, or plain roentgenographic criteria.

  4. Elevated temperature aluminum alloys

    NASA Technical Reports Server (NTRS)

    Meschter, Peter (Inventor); Lederich, Richard J. (Inventor); O'Neal, James E. (Inventor)

    1989-01-01

    Three aluminum-lithium alloys are provided for high performance aircraft structures and engines. All three alloys contain 3 wt % copper, 2 wt % lithium, 1 wt % magnesium, and 0.2 wt % zirconium. Alloy 1 has no further alloying elements. Alloy 2 has the addition of 1 wt % iron and 1 wt % nickel. Alloy 3 has the addition of 1.6 wt % chromium to the shared alloy composition of the three alloys. The balance of the three alloys, except for incidentql impurities, is aluminum. These alloys have low densities and improved strengths at temperatures up to 260.degree. C. for long periods of time.

  5. Identification of a physical metallurgy surrogate for the plutonium—1 wt. % gallium alloy

    NASA Astrophysics Data System (ADS)

    Gibbs, Frank E.; Olson, David L.; Hutchinson, William

    2000-07-01

    Future plutonium research is expected to be limited due to the downsizing of the nuclear weapons complex and an industry focus on environmental remediation and decommissioning of former manufacturing and research facilities. However, the need to further the understanding of the behavior of plutonium has not diminished. Disposition of high level residues, long-term storage of wastes, and certification of the nuclear stockpile through the Stockpile Stewardship Program are examples of the complex issues that must be addressed. Limited experimental facilities and the increasing cost of conducting plutonium research provide a strong argument for the development of surrogate materials. The purpose of this work was to identify a plutonium surrogate based on fundamental principles such as electronic structure, and then to experimentally demonstrate its viability.

  6. Magnetic Domains in Magnetostrictive Fe-Ga Alloys

    SciTech Connect

    Q. Xing; T.A. Lograsso

    2008-11-03

    Lorentz microscopy was applied to the observation of magnetic domains in iron-gallium (Fe-Ga) alloys. Results did not show any link between the magnetic domains and the magnetostriction enhancement by Ga addition, but did reveal that the drastic decrease in magnetostriction for Fe-31.2 at. % Ga was due to the presence of large scale precipitates. Magnetic domain features did not change in the alloys of A2, D0{sub 3}, A2+D0{sub 3}, A2+B2+D0{sub 3}, and A2+fine scale precipitates. Large scale precipitates within the slow-cooled Fe-31.2 at. % Ga affected both the distribution and wall motion of magnetic domains.

  7. Polycrystalline Thin-Film Research: Copper Indium Gallium Diselenide (Fact Sheet)

    SciTech Connect

    Not Available

    2011-06-01

    Capabilities fact sheet for the National Center for Photovoltaics: Polycrystalline Thin-Film Research: Copper Indium Gallium Diselenide that includes scope, core competencies and capabilities, and contact/web information.

  8. Process for producing gallium-containing solution from the aluminum smelting dust

    SciTech Connect

    Era, A.; Matsui, S.; Ikeda, H.

    1988-03-01

    A process is described for producing a gallium-containing solution from aluminum smelting dust comprising leaching aluminum smelting dust with a mineral acid selected from the group consisting of sulfuric acid, hydrochloric acid and nitric acid, and adding an oxidizing agent to the aluminum smelting dust at the time of leaching to preferentially leach and extract gallium from the aluminum smelting dust without extracting aluminum from the aluminum smelting dust. The oxidizing agent is selected from the group consisting of potassium permanganate, manganese dioxide, hydrogen peroxide, ozone, potassium chromate, potassium dichromate, ammonium persulfate, sodium hydrochlorite, sodium chlorite and sodium chlorate. The leached aluminum smelting dust is filtered to obtain a gallium-containing solution of dissolved gallium.

  9. Influence of neodymium concentration on excitation and emission properties of Nd doped gallium oxide nanocrystalline films

    SciTech Connect

    Podhorodecki, A.; Banski, M.; Misiewicz, J.; Lecerf, C.; Marie, P.; Cardin, J.; Portier, X.

    2010-09-15

    Gallium oxide and more particularly {beta}-Ga{sub 2}O{sub 3} matrix is an excellent material for new generation of devices electrically or optically driven as it is known as the widest band gap transparent conductive oxide. In this paper, the optical properties of neodymium doped gallium oxide films grown by magnetron sputtering have been analyzed. The influence of the Nd ions concentration on the excitation/emission mechanisms of Nd ions and the role of gallium oxide matrix have been investigated. The grain size reduction into gallium oxide films have been observed when concentration of Nd increases. It has been found for all samples that the charge transfer is the main excitation mechanism for Nd ions where defect states play an important role as intermediate states. As a consequence Nd emission efficiency increases with temperature giving rise to most intensive emission at 1087 nm at room temperature.

  10. Influence of neodymium concentration on excitation and emission properties of Nd doped gallium oxide nanocrystalline films

    NASA Astrophysics Data System (ADS)

    Podhorodecki, A.; Banski, M.; Misiewicz, J.; Lecerf, C.; Marie, P.; Cardin, J.; Portier, X.

    2010-09-01

    Gallium oxide and more particularly β-Ga2O3 matrix is an excellent material for new generation of devices electrically or optically driven as it is known as the widest band gap transparent conductive oxide. In this paper, the optical properties of neodymium doped gallium oxide films grown by magnetron sputtering have been analyzed. The influence of the Nd ions concentration on the excitation/emission mechanisms of Nd ions and the role of gallium oxide matrix have been investigated. The grain size reduction into gallium oxide films have been observed when concentration of Nd increases. It has been found for all samples that the charge transfer is the main excitation mechanism for Nd ions where defect states play an important role as intermediate states. As a consequence Nd emission efficiency increases with temperature giving rise to most intensive emission at 1087 nm at room temperature.

  11. Ultrasonic cavitation of molten gallium: formation of micro- and nano-spheres.

    PubMed

    Kumar, Vijay Bhooshan; Gedanken, Aharon; Kimmel, Giora; Porat, Ze'ev

    2014-05-01

    Pure gallium has a low melting point (29.8°C) and can be melted in warm water or organic liquids, thus forming two immiscible liquid phases. Irradiation of this system with ultrasonic energy causes cavitation and dispersion of the molten gallium as microscopic spheres. The resultant spheres were found to have radii range of 0.2-5 μm and they do not coalesce upon cessation of irradiation, although the ambient temperature is well above the m.p. of gallium. It was found that the spheres formed in water are covered with crystallites of GaO(OH), whereas those formed in organic liquids (hexane and n-dodecane) are smooth, lacking such crystallites. However, Raman spectroscopy revealed that the spheres formed in organic liquids are coated with a carbon film. The latter may be the factor preventing their coalescence at temperatures above the m.p. of gallium. PMID:24296070

  12. Homogeneous dispersion of gallium nitride nanoparticles in a boron nitride matrix by nitridation with urea.

    PubMed

    Kusunose, Takafumi; Sekino, Tohru; Ando, Yoichi

    2010-07-01

    A Gallium Nitride (GaN) dispersed boron nitride (BN) nanocomposite powder was synthesized by heating a mixture of gallium nitrate, boric acid, and urea in a hydrogen atmosphere. Before heat treatment, crystalline phases of urea, boric acid, and gallium nitrate were recognized, but an amorphous material was produced by heat treatment at 400 degrees C, and then was transformed into GaN and turbostratic BN (t-BN) by further heat treatment at 800 degrees C. TEM obsevations of this composite powder revealed that single nanosized GaN particles were homogeneously dispersed in a BN matrix. Homogeneous dispersion of GaN nanoparticles was thought to be attained by simultaneously nitriding gallium nitrate and boric acid to GaN and BN with urea. PMID:21128417

  13. Gallium-67 scintigraphy, bronchoalveolar lavage, and pathologic changes in patients with pulmonary sarcoidosis

    SciTech Connect

    Abe, S.; Munakata, M.; Nishimura, M.; Tsuneta, Y.; Terai, T.; Nakano, I.; Ohsaki, Y.; Kawakami, Y.

    1984-05-01

    The intensity of gallium-67 scintiscans, lymphocyte counts in bronchoalveolar lavage fluid, and pathologic changes were studied in 26 patients with untreated pulmonary sarcoidosis. Noncaseating granulomas were recognized with significantly greater frequency in stage 2 (80 percent; 8/10 cases) than in stage 1 (43 percent; 6/14 cases). Alveolitis showed little relation to the roentgenographic stage. There was a strong correlation between the intensity of gallium uptake in pulmonary parenchyma and the detection rate of granuloma; however, the detection rate of alveolitis was not statistically different from the intensity of gallium uptake. A highly significant correlation was revealed between the lymphocyte counts in bronchoalveolar lavage fluid and the intensity of alveolitis. These observations suggest that the gallium uptake reflects mainly the presence of granuloma, and the lymphocyte count in bronchoalveolar lavage fluid reflects the intensity of alveolitis in patients with pulmonary sarcoidosis.

  14. A Monte Carlo investigation of Gallium and Arsenic migration on GaAs(100) surface

    NASA Astrophysics Data System (ADS)

    Amrani, A.; Djafari Rouhani, M.; Mraoufel, A.

    2011-05-01

    We perform an atomic scale simulation of GaAs/GaAs(100) growth, using the Kinetic Monte Carlo (KMC) technique, to investigate some aspects of Gallium and Arsenic surface migration. We show that the interlayer migration rate is smaller for Arsenic than for Gallium. Results suggest that upward diffusion is thermally activated while downward diffusion is kinetically controlled. We also find an oscillatory behavior of the surface diffusion rates during the growth, in close relation to the roughening of the substrate. The surface migration rates are governed by the temperature, but mostly by the Arsenic to Gallium flux ratio. The Gallium average diffusion lengths are estimated to be ~440 nm at 620°C and ~130 nm at 530°C, in agreement with experimental data.

  15. Empyema of the gallbladder detected by gallium scan and abdominal ultrasonography

    SciTech Connect

    Garcia, O.M.; Kovac, A.; Plauche, W.E.

    1981-08-01

    A case history of patient with a abnormal gallium uptake and sonogram in the region of the gallbladder is described. The abnormality was interpreted as empyema of the gallbladder and later proven surgically. A liver-spleen scan was normal except for slight prominence of the hilar structures. Gallium citrate Ga-67 scans done at 24 and 48 hours showed a persistent area of increased tracer localization around the gallbladder with a central clear zone in the latter scan. Ultrasonography revealed poor definition and slight thickening of the gallbladder wall. Because of the lack of specificity of gallium scans, the combination of ultrasonic imaging and gallium uptake scans appears much superior in diagnostic efficiency than either of the two alone. The sequence of performing these two examinations does not seem to be critical though it was prefered that the scintigraphy precede the sonography.

  16. Gallium Content in PuO{sub 2} Using Laser Induced Breakdown Spectroscopy (LIBS)

    SciTech Connect

    Smith, C.A.; Martinez, M.A.; Veirs, D.K.

    1999-08-29

    Laser Induced Breakdown Spectroscopy (LIBS) has been applied to the semi-quantitative analysis of gallium in plutonium oxide at the Los Alamos Plutonium Facility. The oxide samples were generated by the Thermally Induced Gallium Removal (TIGR) process, a pretreatment step prior to MOX fuel processing. The TIGR process uses PuO{sub 2} containing 1 wt% gallium (nominal) as feed material. Following the TIGR process, gallium content was analyzed by LIBS and also by conventional wet chemical analysis (ICP-MS). Although the data range was insufficient to obtain an adequate calibration, general agreement between the two techniques was good. LIBS was found to have a useful analytical range of 34-400 ppm for Ga in PuO{sub 2}.

  17. Near-electrode processes in lanthanum-gallium tantalate crystals

    SciTech Connect

    Buzanov, O. A.; Zabelina, E. V. Kozlova, N. S. Sagalova, T. B.

    2008-09-15

    The near-electrode processes on the surfaces of the polar cuts of lanthanum-gallium tantalate crystals grown in different atmospheres were investigated. The temperature dependences of short-circuit currents in the temperature range 20-700{sup o}C were measured and phase analysis of the sample surfaces after the temperature tests were performed. It is shown that short-circuit currents arise on the surfaces of polar cuts with identical conducting coatings without preliminary polarization. These currents are caused by the generation of intrinsic emf as a result of the electrochemical reactions on opposite polar cut surfaces coming in contact with a conducting coating. It is established that the crystal growth atmosphere and the conducting coating material significantly affect the temperature dependences of short-circuit currents.

  18. Investigation of Gadolinium Gallium Oxide using spectroscopic ellipsometry

    NASA Astrophysics Data System (ADS)

    Bhatnagar, Kunal; Sauncy, Toni; Droopad, Ravi

    2010-03-01

    Spectroscopic Ellipsometry (SE) is a non-destructive characterization technique used for determining film thickness, interfacial roughness and optical properties of single and multilayered materials. SE measures the change in the polarization state of the incident light upon reflection from these layers providing insight into the properties and composition of topmost and underlying materials. The Horiba Jobin Yvon - UVISEL located in the Angelo State Materials Characterization Lab is based on the principle of phase modulated spectroscopic ellipsometry. This tool has been used to successfully characterize a variety of semiconductor samples. We will detail results from semiconductor heterostructures containing Gadolinium Gallium Oxide (GdGaO3), a novel material with promise for application as a high-k dielectric in the design of compound semiconductor MOSFETs. Models for this unusual material have been developed and used to characterize various structures with success. We have obtained reasonable values for electrical and optical parameters for the GGO not found in current literature.

  19. Spectroscopic ellipsometric studies of randomly distributed plasmonic Gallium nanoparticles

    NASA Astrophysics Data System (ADS)

    Yang, Yang; Kim, Tong-Ho; Akozbek, Neset; Brown, April; Everitt, Henry

    2013-03-01

    Ultraviolet surfaced-enhanced Raman scattering (UV-SERS) was recently observed using randomly distributed Gallium nanoparticles (Ga NPs) deposited on sapphire by molecular beam expitaxy at room temperature. Atomic force and scanning electron microscopies revealed that the radii of the hemispheroid NPs follow unimodal or bimodal pseudo Gaussian distributions whose mean diameters increase with increasing Ga dosage (i.e. growth time). Variable angle spectroscopic ellipsometric measurements were then performed on Ga NP ensembles to explore the correlation between the polarimetric optical response and the local morphology. An effective medium composed of single or double Lorentzian oscillators was found to reproduce the optical response of Ga NP ensembles with resonance frequencies that decrease monotonically with increasing NP size. In addition, a strong depolarization response was observed for near-normal incidence. Interestingly, the sample for which the depolarization peak was closest to the 325nm laser excitation wavelength was the sample with the highest SERS enhancement factor.

  20. Localized surface phonon polariton resonances in polar gallium nitride

    NASA Astrophysics Data System (ADS)

    Feng, Kaijun; Streyer, William; Islam, S. M.; Verma, Jai; Jena, Debdeep; Wasserman, Daniel; Hoffman, Anthony J.

    2015-08-01

    We demonstrate the excitation of localized surface phonon polaritons in an array of sub-diffraction pucks fabricated in an epitaxial layer of gallium nitride (GaN) on a silicon carbide (SiC) substrate. The array is characterized via polarization- and angle-dependent reflection spectroscopy in the mid-infrared, and coupling to several localized modes is observed in the GaN Reststrahlen band (13.4-18.0 μm). The same structure is simulated using finite element methods and the charge density of the modes are studied; transverse dipole modes are identified for the transverse electric and magnetic polarizations and a quadrupole mode is identified for the transverse magnetic polarization. The measured mid-infrared spectrum agrees well with numerically simulated spectra. This work could enable optoelectronic structures and devices that support surface modes at mid- and far-infrared wavelengths.

  1. Modeling and simulation of bulk gallium nitride power semiconductor devices

    NASA Astrophysics Data System (ADS)

    Sabui, G.; Parbrook, P. J.; Arredondo-Arechavala, M.; Shen, Z. J.

    2016-05-01

    Bulk gallium nitride (GaN) power semiconductor devices are gaining significant interest in recent years, creating the need for technology computer aided design (TCAD) simulation to accurately model and optimize these devices. This paper comprehensively reviews and compares different GaN physical models and model parameters in the literature, and discusses the appropriate selection of these models and parameters for TCAD simulation. 2-D drift-diffusion semi-classical simulation is carried out for 2.6 kV and 3.7 kV bulk GaN vertical PN diodes. The simulated forward current-voltage and reverse breakdown characteristics are in good agreement with the measurement data even over a wide temperature range.

  2. A model for pore growth in anodically etched gallium phosphide

    NASA Astrophysics Data System (ADS)

    Ricci, P. C.; Salis, M.; Anedda, A.

    2005-06-01

    The electrochemical etching process of porous gallium phosphide was studied by means of the characteristic current-potential (I-V) curves. Measurements were performed in H2SO4 0.5-M aqueous solution both in the dark and by illuminating the samples with the 351-nm line of an argon laser. Raman spectroscopy was applied to investigate the surface morphology of the samples prepared under different anodizing conditions within the potentiostatic regime. Based on a few reasonable assumptions, a simple model of pore growth is proposed. The enhancing effect in current intensity due to the branching of pores and the opposite effect due to a concomitant decrease in the effective cross area available for carrier transport are accounted for to explain the main features of the recorded I -V curves.

  3. Electron microscopy of gallium nitride growth on polycrystalline diamond

    NASA Astrophysics Data System (ADS)

    Webster, R. F.; Cherns, D.; Kuball, M.; Jiang, Q.; Allsopp, D.

    2015-11-01

    Transmission and scanning electron microscopy were used to examine the growth of gallium nitride (GaN) on polycrystalline diamond substrates grown by metalorganic vapour phase epitaxy with a low-temperature aluminium nitride (AlN) nucleation layer. Growth on unmasked substrates was in the (0001) orientation with threading dislocation densities ≈7 × 109 cm-2. An epitaxial layer overgrowth technique was used to reduce the dislocation densities further, by depositing silicon nitride stripes on the surface and etching the unmasked regions down to the diamond substrate. A re-growth was then performed on the exposed side walls of the original GaN growth, reducing the threading dislocation density in the overgrown regions by two orders of magnitude. The resulting microstructures and the mechanisms of dislocation reduction are discussed.

  4. Temperature dependence of carrier capture by defects in gallium arsenide

    SciTech Connect

    Wampler, William R.; Modine, Normand A.

    2015-08-01

    This report examines the temperature dependence of the capture rate of carriers by defects in gallium arsenide and compares two previously published theoretical treatments of this based on multi phonon emission (MPE). The objective is to reduce uncertainty in atomistic simulations of gain degradation in III-V HBTs from neutron irradiation. A major source of uncertainty in those simulations is poor knowledge of carrier capture rates, whose values can differ by several orders of magnitude between various defect types. Most of this variation is due to different dependence on temperature, which is closely related to the relaxation of the defect structure that occurs as a result of the change in charge state of the defect. The uncertainty in capture rate can therefore be greatly reduced by better knowledge of the defect relaxation.

  5. Recognition of distinctive patterns of gallium-67 distribution in sarcoidosis

    SciTech Connect

    Sulavik, S.B.; Spencer, R.P.; Weed, D.A.; Shapiro, H.R.; Shiue, S.T.; Castriotta, R.J. )

    1990-12-01

    Assessment of gallium-67 ({sup 67}Ga) uptake in the salivary and lacrimal glands and intrathoracic lymph nodes was made in 605 consecutive patients including 65 with sarcoidosis. A distinctive intrathoracic lymph node {sup 67}Ga uptake pattern, resembling the Greek letter lambda, was observed only in sarcoidosis (72%). Symmetrical lacrimal gland and parotid gland {sup 67}Ga uptake (panda appearance) was noted in 79% of sarcoidosis patients. A simultaneous lambda and panda pattern (62%) or a panda appearance with radiographic bilateral, symmetrical, hilar lymphadenopathy (6%) was present only in sarcoidosis patients. The presence of either of these patterns was particularly prevalent in roentgen Stages I (80%) or II (74%). We conclude that simultaneous (a) lambda and panda images, or (b) a panda image with bilateral symmetrical hilar lymphadenopathy on chest X-ray represent distinctive patterns which are highly specific for sarcoidosis, and may obviate the need for invasive diagnostic procedures.

  6. Design and Performance Estimates of an Ablative Gallium Electromagnetic Thruster

    NASA Technical Reports Server (NTRS)

    Thomas, Robert E.

    2012-01-01

    The present study details the high-power condensable propellant research being conducted at NASA Glenn Research Center. The gallium electromagnetic thruster is an ablative coaxial accelerator designed to operate at arc discharge currents in the range of 10-25 kA. The thruster is driven by a four-parallel line pulse forming network capable of producing a 250 microsec pulse with a 60 kA amplitude. A torsional-type thrust stand is used to measure the impulse of a coaxial GEM thruster. Tests are conducted in a vacuum chamber 1.5 m in diameter and 4.5 m long with a background pressure of 2 microtorr. Electromagnetic scaling calculations predict a thruster efficiency of 50% at a specific impulse of 2800 seconds.

  7. Compilation of gallium resource data for bauxite deposits

    USGS Publications Warehouse

    Schulte, Ruth F.; Foley, Nora K.

    2014-01-01

    Gallium (Ga) concentrations for bauxite deposits worldwide have been compiled from the literature to provide a basis for research regarding the occurrence and distribution of Ga worldwide, as well as between types of bauxite deposits. In addition, this report is an attempt to bring together reported Ga concentration data into one database to supplement ongoing U.S. Geological Survey studies of critical mineral resources. The compilation of Ga data consists of location, deposit size, bauxite type and host rock, development status, major oxide data, trace element (Ga) data and analytical method(s) used to derive the data, and tonnage values for deposits within bauxite provinces and districts worldwide. The range in Ga concentrations for bauxite deposits worldwide is

  8. Coated gallium arsenide neutron detectors : results of characterizationmeasurements.

    SciTech Connect

    Klann, R. T.; Perret, G.; Sanders, J.

    2006-09-29

    Effective detection of special nuclear materials (SNM) is essential for reducing the threat associated with stolen or improvised nuclear devices. Passive radiation detection technologies are primarily based on gamma-ray detection and subsequent isotope identification or neutron detection (specific to neutron sources and SNM). One major effort supported by the Department of Homeland Security in the area of advanced passive detection is handheld or portable neutron detectors for search and localization tasks in emergency response and interdiction settings. A successful SNM search detector will not only be able to confirm the presence of fissionable materials but also establish the location of the source in as short of time as possible while trying to minimize false alarms due to varying background or naturally occurring radioactive materials (NORM). For instruments based on neutron detectors, this translates to detecting neutrons from spontaneous fission or alpha-n reactions and being able to determine the direction of the source (or localizing the source through subsequent measurements). Polyethylene-coated gallium arsenide detectors were studied because the detection scheme is based on measuring the signal in the gallium arsenide wafers from the electrical charge of the recoil protons produced from the scattering of neutrons from the hydrogen nucleus. The inherent reaction has a directional dependence because the neutron and hydrogen nucleus have equivalent masses. The assessment and measurement of polyethylene-coated gallium arsenide detector properties and characteristics was the first phase of a project being performed for the Department of Homeland Security and the results of these tests are reported in this report. The ultimate goal of the project was to develop a man-portable neutron detection system that has the ability to determine the direction of the source from the detector. The efficiency of GaAs detectors for different sizes of polyethylene layers and different angles between the detector and the neutron source were determined. Preliminary measurements with a neutron generator based on a deuterium-tritium reaction ({approx}14 MeV neutrons) were performed and the results are discussed. This report presents the results of these measurements in terms of efficiency and angular efficiency and compares them to Monte Carlo calculations to validate the calculation scheme in view of further applications. Based on the results of this study, the polyethylene-coated gallium arsenide detectors provide adequate angular resolution based on proton recoil detection from the neutron scattering reaction from hydrogen. However, the intrinsic efficiency for an individual detector is extremely low. Because of this low efficiency, large surface area detectors ( or a large total surface area from many small detectors) would be required to generate adequate statistics to perform directional detection in near-real time. Large surface areas could be created by stacking the detector wafers with only a negligible attenuation of source neutrons. However, the cost of creating such a large array of GaAs is cost-prohibitive at this time.

  9. Single event upsets in gallium arsenide dynamic logic

    SciTech Connect

    Fouts, D.J. . ECE Dept.); Weatherford, T. ); McMorrow, C.; Melinger, J.S.; Campbell, A.B. )

    1994-12-01

    The advantages and disadvantages of using gallium arsenide (GaAs) dynamic logic in computers and digital systems are briefly discussed, especially with respect to space applications. A short introduction to the topology and operation of GaAs Two-Phase Dynamic FET Logic (TDFL) circuits is presented. Experiments for testing the SEU sensitivity of GaAs TDFL, using a laser to create charge collection events, are described. Results are used to estimate the heavy-ion, soft error rate for TDFL in a spacecraft in geosynchronous orbit, and the dependence of the SEU sensitivity on clock frequency, clock voltage, and clock phase. Analysis of the data includes a comparison between the SEU sensitivities of TDFL and the more common static form of GaAs logic, Directly Coupled FET Logic (DCFL). This is the first reported SEU testing of GaAs dynamic logic.

  10. Fabrication and properties of gallium phosphide variable colour displays

    NASA Technical Reports Server (NTRS)

    Effer, D.; Macdonald, R. A.; Macgregor, G. M.; Webb, W. A.; Kennedy, D. I.

    1973-01-01

    The unique properties of single-junction gallium phosphide devices incorporating both red and green radiative recombination centers were investigated in application to the fabrication of monolithic 5 x 7 displays capable of displaying symbolic and alphanumeric information in a multicolor format. A number of potentially suitable material preparation techniques were evaluated in terms of both material properties and device performance. Optimum results were obtained for double liquid-phase-epitaxial process in which an open-tube dipping technique was used for n-layer growth and a sealed tipping procedure for subsequent p-layer growth. It was demonstrated that to prepare devices exhibiting a satisfactory range of dominant wavelengths which can be perceived as distinct emission colors extending from the red through green region of the visible spectrum involves a compromise between the material properties necessary for efficient red emission and those considered optimum for efficient green emission.

  11. Low-threshold indium gallium nitride quantum dot microcavity lasers

    NASA Astrophysics Data System (ADS)

    Woolf, Alexander J.

    Gallium nitride (GaN) microcavities with embedded optical emitters have long been sought after as visible light sources as well as platforms for cavity quantum electrodynamics (cavity QED) experiments. Specifically, materials containing indium gallium nitride (InGaN) quantum dots (QDs) offer an outstanding platform to study light matter interactions and realize practical devices, such as on-chip light emitting diodes and nanolasers. Inherent advantages of nitride-based microcavities include low surface recombination velocities, enhanced room-temperature performance (due to their high exciton binding energy, as high as 67 meV for InGaN QDs), and emission wavelengths in the blue region of the visible spectrum. In spite of these advantages, several challenges must be overcome in order to capitalize on the potential of this material system. Such diffculties include the processing of GaN into high-quality devices due to the chemical inertness of the material, low material quality as a result of strain-induced defects, reduced carrier recombination effciencies due to internal fields, and a lack of characterization of the InGaN QDs themselves due to the diffculty of their growth and therefore lack of development relative to other semiconductor QDs. In this thesis we seek to understand and address such issues by investigating the interaction of light coupled to InGaN QDs via a GaN microcavity resonator. Such coupling led us to the demonstration of the first InGaN QD microcavity laser, whose performance offers insights into the properties and current limitations of the nitride materials and their emitters. This work is organized into three main sections. Part I outlines the key advantages and challenges regarding indium gallium nitride (InGaN) emitters embedded within gallium nitride (GaN) optical microcavities. Previous work is also discussed which establishes context for the work presented here. Part II includes the fundamentals related to laser operation, including the derivation and analysis of the laser rate equations. A thorough examination of the rate equations serves as a natural motivation for QDs and high-quality factor low-modal volume resonators as an optimal laser gain medium and cavity, respectively. The combination of the two theoretically yields the most efficient semiconductor laser device possible. Part III describes in detail the design, growth, fabrication and characterization of the first InGaN QD microcavity laser. Additional experiments are also conducted in order to conclusively prove that the InGaN QDs serve as the gain medium and facilitate laser oscillation within the microdisk cavities. Part III continues with work related towards the development of the next generation of nitride light emitting devices. This includes the realization of photonic crystal cavity (PCC) fragmented quantum well (FQW) lasers that exhibit record low lasing thresholds of 9.1 muJ/cm2, comparable to the best devices in other III-V material systems. Part III also discusses cavity QED experiments on InGaN QDs embedded within GaN PCCs in order to quantify the degree of light-matter interaction. The lack of experimental evidence for weak or strong coupling, in the form of the Purcell Effect or cavity-mode anti-crossing respectively, naturally motivates the question of what mechanism is limiting the device performance. Part III concludes with cathodoluminesence and tapered fiber measurements in order to identify the limiting factor towards achieving strong coupling between InGaN QDs and GaN microcavities.

  12. Interplay of disorder and geometrical frustration in Gadolinium Gallium Garnet

    NASA Astrophysics Data System (ADS)

    Woo, Nayoon; Silevitch, D. M.; Rosenbaum, T. F.

    2015-03-01

    We study the effects of disorder on the geometrically frustrated Heisenberg antiferromagnet Gadolinium Gallium Garnet (GGG) using neodymium doping (0.1 to 1%) in combination with linear and nonlinear ac magnetic susceptibility. The Nd doping actually alleviates the effects of disorder due to excess Gd ions occupying Ga sites. The linear, frequency-dependent susceptibility reveals that 1% Nd doping suppresses the appearance of any long-range order from approximately 80mK to below 30mK. The dynamics of isolated, correlated spin clusters were studied as a function of doping level using nonlinear susceptometry. In this regime, both the aggregate moment of the clustered spins and the activation field required to excite a nonlinear response were inversely correlated with the dopant density.

  13. A study of surface tension driven segregation in monotectic alloy systems

    NASA Technical Reports Server (NTRS)

    Andrews, J. Barry; Andrews, Rosalia N.; Gowens, Terrell F.

    1988-01-01

    The compatibilities of various monotectic alloy systems with several different crucible materials were evaluated. The study was carried out using small candidate alloy samples of compositions that produced fifty volume percent of each liquid phase at the monotectic temperature. Compatibility was based on the evaluation of the wetting tendency of the two immiscible phases with the crucible material in a one-g solidified sample. Three types of wetting phenomena were observed during the evaluation. Type 1 indicates an alloy-crucible combination where the L2 phase preferentially wets the crucible material. Since L2 is usually the minority phase in desirable alloys, this material combination would be difficult to process and is therefore considered incompatible. Type 2 behavior indicates an alloy-crucible combination where the L1 phase preferentially wets the crucible material. This type of combination is considered compatible since surface tension effects should aid in processing the alloy to a useful form. Type 3 indicates any combination that leads to major reactions between the alloy and crucible material, gas entrapment, or separation of the metal from the crucible wall. Additional compatibility evaluations would have to be carried out on combinations of this category. The five alloy systems studied included aluminum-bismuth, copper-lead, aluminum-indium, aluminum-lead and cadmium-gallium. The systems were combined with crucibles of alumina, boron nitride, mullite, quartz, silicon carbide and zirconia.

  14. Determination of Hg traces in gallium by anodic stripping voltametry on glassy carbon

    SciTech Connect

    Pezzatini, G.; Pergola, F.

    1986-01-01

    An A.S.V. (anodic stripping voltametry) method for determination of mercury in ultrapure gallium has been developed. The procedure is very simple and allows a sensitivity high enough to verify the highest purity level of Ga as concerns Hg traces (i.e. 1 x 10/sup -5/ % Hg in Ga by weight). The above method was applied to some samples of gallium used in this laboratory. 15 references, 3 figures.

  15. Gallium compounds in solar cells. (Latest citations from the Aerospace database). Published Search

    SciTech Connect

    Not Available

    1993-12-01

    The bibliography contains citations concerning the use of gallium compounds in solar cells to increase solar cell efficiency. Computer models, theories, and performance tests are included. Gallium compounds used in thin film cells, cascade solar cells, large area solar cells, cells designed for industrial and space applications, and as antireflection coatings are discussed. Resistance to radiation damage, cooling to improve efficiency, grain boundary behavior, and economic considerations are also covered. (Contains 250 citations and includes a subject term index and title list.)

  16. Gallium scanning and tomography in the preoperative evaluation of lung cancer

    SciTech Connect

    Santiago, S.; Houston, D.; Ezer, J.; Rose, J.; Nagai, E.; Williams, A.

    1986-07-15

    Discrepant reports on the utility of gallium scanning in the preoperative evaluation of patients with lung cancer prompted a prospective study of the test. The authors studied 47 patients with lung cancer who underwent preoperative gallium scanning and frontal tomography of the mediastinum. Both tests were found to be most accurate in predicting the presence of mediastinal metastases among patients with squamous cell carcinoma. Both test may help direct surgical planning in patients with known squamous cell carcinoma of the lung.

  17. First Results of the Testing of the Liquid Gallium Jet Limiter Concept for ISTTOK

    NASA Astrophysics Data System (ADS)

    Gomes, R. B.; Fernandes, H.; Silva, C.; Borba, D.; Carvalho, B.; Varandas, C.; Lielausis, O.; Klyukin, A.; Platacis, E.; Mikelsons, A.; Platnieks, I.

    2006-12-01

    The use of liquid metals as plasma facing components in tokamaks has recently experienced a renewed interest stimulated by their advantages to the development of a fusion reactor. Liquid metals have been proposed to solve problems related to the erosion and neutronic activation of solid walls submitted to high power loads allowing an efficient heat exhaustion from fusion devices. Presently the most promising materials are Lithium and Gallium. ISTTOK, a small size tokamak, will be used to test the behavior of a liquid Gallium jet in the vacuum chamber and its influence on the plasma. This paper presents a description of the conceived setup as well as experimental results. The liquid Gallium jet is generated by hydrostatic pressure and injected in a radial position close to a moveable stainless steel limiter. Both the jet and the limiter positions are variable allowing for a controlled exposure of the liquid Gallium to the edge plasma. The main components of the Gallium loop are a MHD pump, the liquid metal injector and a filtering system. The MHD pump is of the induction type, based on rotating permanent magnets. The injector is build from a ¼″ stainless steel pipe ended by a shaping nozzle. A setup has been developed to introduce oxide-free Gallium inside the loop's main supply tank. Raw liquid metal is placed inside a chamber heated and degassed under high vacuum while clean Gallium is extracted from the main body of the liquefied metal. Prior to installation on the tokamak, the experimental rig has been implemented using a Pyrex tube as test chamber to investigate the stability of the Gallium jet and its break-up length for several nozzle sizes. Results are presented in this paper. This rig was also useful to assess the behavior of the overall implemented apparatus.

  18. Bit-systolic arithmetic arrays using dynamic differential gallium arsenide circuits

    NASA Technical Reports Server (NTRS)

    Beagles, Grant; Winters, Kel; Eldin, A. G.

    1992-01-01

    A new family of gallium arsenide circuits for fine grained bit-systolic arithmetic arrays is introduced. This scheme combines features of two recent techniques of dynamic gallium arsenide FET logic and differential dynamic single-clock CMOS logic. The resulting circuits are fast and compact, with tightly constrained series FET propagation paths, low fanout, no dc power dissipation, and depletion FET implementation without level shifting diodes.

  19. Haemophilus parainfluenzae bacteremia associated with a pacemaker wire localized by gallium scan

    SciTech Connect

    Rosenbaum, G.S.; Calubiran, O.; Cunha, B.A. )

    1990-05-01

    A young woman with a history of sick sinus syndrome and placement of a permanent pacemaker 6 months before admission had fever and Haemophilus parainfluenzae bacteremia. A gallium scan localized the infection to the site of the pacemaker wire. Echocardiograms were negative for any vegetations. The patient responded to cefotaxime and trimethoprim-sulfamethoxazole therapy. We believe that this is the first case of H. parainfluenzae bacteremia associated with a pacemaker wire and localized by gallium scan.

  20. Heterotopic ossification (myositis ossificans) in acquired immune deficiency syndrome. Detection by gallium scintigraphy

    SciTech Connect

    Drane, W.E.; Tipler, B.M.

    1987-06-01

    A case of heterotopic ossification (myositis ossificans) secondary to the central nervous system complications of acquired immune deficiency syndrome (AIDS) is reported. Because of the overwhelming suspicion of infection in this patient, this diagnosis was not considered until a gallium scan revealed the typical findings of heterotopic ossification. Because of the increasing utilization of gallium imaging in the AIDS population, every imaging specialist should be aware of this potential disorder.

  1. Sequential technetium-99m/gallium-67 scintigraphic evaluation of subclinical osteomyelitis complicating fracture nonunion

    SciTech Connect

    Esterhai, J.; Alavi, A.; Mandell, G.A.; Brown, J.

    1985-01-01

    Twenty-four patients with a history of post-traumatic fracture nonunion underwent sequential /sup 99m/Tc and /sup 67/Ga citrate scintigraphy in an attempt to differentiate between posttraumatic fracture nonunion and nonunion complicated by subclinical osteomyelitis. Neither technetium nor gallium studies alone nor in combination, with or without clinical correlation, could help delineate between fracture nonunion and nonunion complicated by subclinical osteomyelitis because of the increased technetium and gallium radioisotope uptake associated with the nonunion site.

  2. Tumoral calcinosis associated with sarcoidosis and positive bone and gallium imaging

    SciTech Connect

    Wolpe, F.M.; Khedkar, N.Y.; Gordon, D.; Werner, P.; Shirazi, P.; Al-Sabban, M.H.

    1987-07-01

    A 63-year-old female with biopsy proven tumoral calcinosis presented with progressive and recurrent swelling and tenderness of the right hip, thigh, elbow, and wrist. Both gallium and bone imaging demonstrated intense, congruent uptake in these areas. This is the third case of tumoral calcinosis with sarcoidosis documented in the literature. However, these are the first published bone and gallium scans in a patient with a history of sarcoidosis and tumoral calcinosis.

  3. Study of Magnetohydrodynamic Surface Waves on Liquid Gallium

    SciTech Connect

    Hantao Ji; William Fox; David Pace; H.L. Rappaport

    2004-05-13

    Magnetohydrodynamic (MHD) surface waves on liquid gallium are studied theoretically and experimentally in the small magnetic Reynolds number limit. A linear dispersion relation is derived when a horizontal magnetic field and a horizontal electric current is imposed. No wave damping is found in the shallow liquid limit while waves always damp in the deep liquid limit with a magnetic field parallel to the propagation direction. When the magnetic field is weak, waves are weakly damped and the real part of the dispersion is unaffected, while in the opposite limit waves are strongly damped with shortened wavelengths. In a table-top experiment, planar MHD surface waves on liquid gallium are studied in detail in the regime of weak magnetic field and deep liquid. A non-invasive diagnostic accurately measures surface waves at multiple locations by reflecting an array of lasers off the surface onto a screen, which is recorded by an Intensified-CCD camera. The measured dispersion relation is consistent with the linear theory with a reduced surface tension likely due to surface oxidation. In excellent agreement with linear theory, it is observed that surface waves are damped only when a horizontal magnetic field is imposed parallel to the propagation direction. No damping is observed under a perpendicular magnetic field. The existence of strong wave damping even without magnetic field suggests the importance of the surface oxide layer. Implications to the liquid metal wall concept in fusion reactors, especially on the wave damping and a Rayleigh-Taylor instability when the Lorentz force is used to support liquid metal layer against gravity, are discussed.

  4. Novel ethylenediamine-gallium phosphate containing 6-fold coordinated gallium atoms with unusual four equatorial Ga–N bonds

    SciTech Connect

    Torre-Fernández, Laura; Espina, Aránzazu; Khainakov, Sergei A.; Amghouz, Zakariae; García, José R.; García-Granda, Santiago

    2014-07-01

    A novel ethylenediamine-gallium phosphate, formulated as Ga(H{sub 2}NCH{sub 2}CH{sub 2}NH{sub 2}){sub 2}PO{sub 4}·2H{sub 2}O, was synthesized under hydrothermal conditions. The crystal structure, including hydrogen positions, was determined using single-crystal X-ray diffraction data (monoclinic, a=9.4886(3) Å, b=6.0374(2) Å, c=10.2874(3) Å, and β=104.226(3)°, space group Pc) and the bulk was characterized by chemical (Ga–P–C–H–N) and thermal analysis (TG–MS and DSC), including activation energy data of its thermo-oxidative degradation, powder X-ray diffraction (PXRD), solid-state nuclear magnetic resonance (SS-NMR) measurements, and transmission electron microscopy (TEM, SAED/NBD, and STEM BF-EDX). The crystal structure is built up of infinite zig-zag chains running along the c-axis, formed by vertex-shared (PO{sub 4}) and (GaO{sub 2}N{sub 4}) polyhedra. The new compound is characterized by unusual four equatorial Ga–N bonds coming from two nonequivalent ethylenediamine molecules and exhibits strong blue emission at 430 nm (λ{sub ex}=350 nm) in the solid state at room temperature. - Graphical abstract: Single crystals of a new ethylenediamine-gallium phosphate, Ga(H{sub 2}NCH{sub 2}CH{sub 2}NH{sub 2}){sub 2}PO{sub 4}·2H{sub 2}O, were obtained and the structural features presented. This structure is one of the scarce examples of GaPO with Ga–N bonds reported. - Highlights: • A novel ethylenediamine-gallium phosphate was hydrothermally synthesized. • The new compound is characterized by unusual four equatorial Ga–N bonds. • Void-volume analysis shows cages and channels with sizes ideally suited to accommodate small molecules. • The new compound exhibits strong blue emission.

  5. Preparation of gallium oxynitride powder and its nanofibers by the nitridation of a gallium oxide precursor doped with nickel or cobalt obtained via the citrate route.

    PubMed

    Miyaake, A; Masubuchi, Y; Takeda, T; Motohashi, T; Kikkawa, S

    2010-07-14

    Acicular crystals were grown in gallium oxynitride powder prepared by ammonia nitridation of amorphous gallium oxide precursors containing less than 5 at% of either Ni or Co, via the citrate route. The crystals were several tens of nanometres wide, several micrometres long, and grown in the temperature range 750 to 850 degrees C in a flow of ammonia of less than 200 mL min(-1). The crystal structure of the gallium oxynitride was a highly disordered 2H wurtzite-type with some 3C zinc blende-type stacking faults. The crystals grew in their basal plane changing their aspect ratio with the supplying method of small amounts of Ni or Co and an amount of residual carbon. The acicular crystals were grown by the catalytic behavior of Ni or Co to enhance one-dimensional growth in the hexagonal c-plane. PMID:20571651

  6. Study of liquid gallium at high pressure using synchrotron x-ray

    NASA Astrophysics Data System (ADS)

    Yu, Tony; Chen, Jiuhua; Ehm, Lars; Huang, Shu; Guo, Quanzhong; Luo, Sheng-Nian; Parise, John

    2012-06-01

    Liquid gallium has been studied at high pressure up to 2 GPa and ambient temperature in a diamond anvil cell using high energy synchrotron x-ray beam. The total x-ray scattering data of liquid gallium were collected up to Q = 12 Å-1 and analyzed using pair distribution functions (PDF). The results indicate that the first nearest neighbor peak and second nearest neighbor (shoulder) peak of PDF in liquid gallium does not change with pressure, whereas the higher order (i.e., third and fourth) nearest neighbor peaks shift towards shorter distance with increasing pressure. Reverse Monte Carlo modeling based on the observed data shows that the coordination number in the liquid gallium increases with pressure from 10.5 at 0.3 GPa to 11.6 at 2 GPa. An atomic arrangement similar to the crystalline phase of Ga(II) with coordination number of 12 is proposed for the locally dense-packed rigid unit in liquid gallium. The volume compression data derived from the structure modeling yield a bulk modulus of 12.1(6) GPa for liquid gallium.

  7. The use of gallium-67 scintigraphy in the diagnosis of acute interstitial nephritis

    PubMed Central

    Graham, François; Lord, Martin; Froment, Daniel; Cardinal, Héloise; Bollée, Guillaume

    2016-01-01

    Background Gallium-67 scintigraphy has been suggested as a noninvasive method to diagnose acute interstitial nephritis (AIN). However, its diagnostic performance and usefulness remain controversial. Methods We retrospectively reviewed the charts of 76 patients who underwent gallium-67 scintigraphy for a suspicion of AIN. Patients were classified based on kidney biopsy and/or clinical probability of AIN. Gallium-67 scintigraphy results were reinterpreted blindly using both posterior planar and single photon emission computed tomography (SPECT) imaging. Intensity of radioisotope uptake in the kidney was graded from 0 to 5. Results The diagnosis of AIN was confirmed in 23 patients and excluded in 44. Nine patients with an uncertain diagnosis were excluded from subsequent analysis. A gallium-67 kidney uptake cutoff of 1 gave a negative predictive value of 100%, whereas a cutoff of 5 had an excellent specificity and positive predictive value for the diagnosis of AIN. When using a cutoff of 3, which had previously been used in the literature, we obtained a sensitivity of 61% and a specificity of 75% with posterior planar imaging. The results of both SPECT and posterior planar imaging modalities were comparable. Conclusions Gallium-67 scintigraphy may be of interest in patients with a clinical suspicion of AIN, especially in those who are unable to undergo kidney biopsy. However, results need to be interpreted with caution and depend on the intensity of gallium-67 kidney uptake. PMID:26798465

  8. Study of liquid gallium at high pressure using synchrotron x-ray

    SciTech Connect

    Yu, Tony; Guo Quanzhong; Parise, John; Chen Jiuhua; Ehm, Lars; Huang Shu; Luo Shengnian

    2012-06-01

    Liquid gallium has been studied at high pressure up to 2 GPa and ambient temperature in a diamond anvil cell using high energy synchrotron x-ray beam. The total x-ray scattering data of liquid gallium were collected up to Q = 12 A{sup -1} and analyzed using pair distribution functions (PDF). The results indicate that the first nearest neighbor peak and second nearest neighbor (shoulder) peak of PDF in liquid gallium does not change with pressure, whereas the higher order (i.e., third and fourth) nearest neighbor peaks shift towards shorter distance with increasing pressure. Reverse Monte Carlo modeling based on the observed data shows that the coordination number in the liquid gallium increases with pressure from 10.5 at 0.3 GPa to 11.6 at 2 GPa. An atomic arrangement similar to the crystalline phase of Ga(II) with coordination number of 12 is proposed for the locally dense-packed rigid unit in liquid gallium. The volume compression data derived from the structure modeling yield a bulk modulus of 12.1(6) GPa for liquid gallium.

  9. High-Temperature Decomposition of Brønsted Acid Sites in Gallium-Substituted Zeolites

    SciTech Connect

    K Al-majnouni; N Hould; W Lonergan; D Vlachos; R Lobo

    2011-12-31

    The dehydroxylation of Broensted acid sites (BAS) in Ga-substituted zeolites was investigated at temperatures up to 850 C using X-ray absorption spectroscopy (XAS), Fourier transform infrared spectroscopy (FTIR), and mass spectrometry-temperature programmed desorption (MS-TPD). X-ray absorption near-edge spectroscopy (XANES) revealed that the majority of gallium has tetrahedral coordination even after complete dehydroxylation. The interatomic gallium-oxygen distance and gallium coordination number determined by extended X-ray absorption fine structure (EXAFS) are consistent with gallium in tetrahedral coordination at low T (< 550 C). Upon heating Ga-Beta and Ga-ZSM5 to 850 C, analysis of the EXAFS showed that 70 and 80% of the gallium was still in tetrahedral coordination. The remainder of the gallium was found to be in octahedral coordination. No trigonal Ga atoms were observed. FTIR measurements carried out at similar temperatures show that the intensity of the OH vibration due to BAS has been eliminated. MS-TPD revealed that hydrogen in addition to water evolved from the samples during dehydroxylation. This shows that dehydrogenation in addition to dehydration is a mechanism that contributes to BAS decomposition. Dehydrogenation was further confirmed by exposing the sample to hydrogen to regenerate some of the BAS as monitored by FTIR and MS-TPD.

  10. Sequential technetium-99m HMDP-gallium-67 citrate imaging for the evaluation of infection in the painful prosthesis

    SciTech Connect

    Merkel, K.D.; Brown, M.L.; Fitzgerald, R.H. Jr.

    1986-09-01

    In order to evaluate the clinical utility of sequential technetium-99m HMDP-gallium-67 scanning in patients with painful orthopedic prosthesis, a retrospective review was made of 154 sequential scans performed in 130 patients. Criteria for a positive study included spatially incongruent gallium-technetium uptake or gallium uptake that was congruent but more intense than technetium. Images were interpreted as negative if gallium was congruent and less intense than technetium. Sixty-six patients underwent surgery (31 infected, 35 aseptic), and 64 were evaluated clinically (3 infected, 61 aseptic). The combined results of the surgical and nonsurgical patients yielded a sensitivity of 66%, a specificity of 81%, and an accuracy of 77%. In this series, the technetium-gallium scan combination has proven to be helpful but more recent techniques such as indium-111-labeled leukocytes may prove to be superior to sequential technetium-gallium imaging.

  11. Concerning the energy levels of silver in Ge-Si alloys

    SciTech Connect

    Tahirov, V. I.; Agamaliev, Z. A.; Sadixova, S. R.; Guliev, A. F.; Gahramanov, N. F.

    2012-03-15

    The emission from impurity states of silver (an element of the IB subgroup) in a Ge-Si alloy, containing 18 at % Si, has been studied. The donor level of silver has been found in crystals doubly doped with gallium and silver, while its first acceptor level has been revealed in crystals doped with only silver. Single crystals were grown by pulling from a melt using a feeding rod. Doping with gallium was performed by introducing this element into the feeding rod, and silver was introduced into the crystals via diffusion. The positions of the donor and first acceptor Ag levels with respect to the top of the valence band were found by analyzing the temperature dependence of the Hall coefficient and the electroneutrality equation for the crystal: 0.06 and 0.29 eV, respectively.

  12. Origin of optical bistability and hysteretic reflectivity on account of nonlinearity at optically induced gallium silica interface

    NASA Astrophysics Data System (ADS)

    Sharma, Arvind; Nagar, A. K.

    2016-05-01

    The origin of optical bistability and hysterectic reflectivity on account of nonlinearity at optically induced Gallium silica interface has been investigated. Assuming the wave to be incident from the gallium nano particle layer side at gallium silica interface. The coupling between incident and reflected waves has shown nonlinear effects on Snell's law and Fresnel law. Effect of these nonlinear processes optical bistability and hysterectic reflectivity theoretically has been investigated. Theoretical results obtained are consistent with the available experimental results.

  13. Growth and analysis of gallium arsenide-gallium antimonide single and two-phase nanoparticles

    NASA Astrophysics Data System (ADS)

    Schamp, Crispin T.

    When evaluating the path of phase transformations in systems with nanoscopic dimensions one often relies on bulk phase diagrams for guidance because of the lack of phase diagrams that show the effect of particle size. The GaAs-GaSb pseudo-binary alloy is chosen for study to gain insight into the size dependence of solid-solubility in a two-phase system. To this end, a study is performed using independent laser ablation of high purity targets of GaAs and GaSb. The resultant samples are analyzed by transmission electron microscopy. Experimental results indicate that GaAs-GaSb nanoparticles have been formed with compositions that lie within the miscibility gap of bulk GaAs-GaSb. An unusual nanoparticle morpohology resembling the appearance of ice cream cones has been observed in single component experiments. These particles are composed of a spherical cap of Ga in contact with a crystalline cone of either GaAs or GaSb. The cones take the projected 2-D shape of a triangle or a faceted gem. The liquid Ga is found to consistently be of spherical shape and wets to the widest corners of the cone, suggesting an energy minimum exists at that wetting condition. To explore this observation a liquid sphere is modeled as being penetrated by a solid gem. The surface energies of the solid and liquid, and interfacial energy are summed as a function of penetration depth, with the sum showing a cusped minimum at the penetration depth corresponding to the waist of the gem. The angle of contact of the liquid wetting the cone is also calculated, and Young's contact angle is found to occur when the derivative of the total energy with respect to penetration depth is zero, which can be a maximum or a minimum depending on the geometrical details. The spill-over of the meniscus across the gem corners is found to be energetically favorable when the contact angle achieves the value of the equilibrium angle; otherwise the meniscus is pinned at the corners.

  14. Understanding the Impact of Point Defects on the Optoelectronic Properties of Gallium Nitride from First-Principles

    NASA Astrophysics Data System (ADS)

    Lewis, Kirk; Matsubara, Masahiko; Bellotti, Enrico; Sharifzadeh, Sahar

    Gallium nitride (GaN) and related alloys form a class of wide bandgap semiconductors that have broad applications as components in optoelectronic devices; in particular, power electronics and blue and ultraviolet optical devices. Nitride films grow with high defect densities, and understanding the relationship between structural defects and optoelectronic function will be central to the design of new high-performance materials. Here, we take a first-principles density functional theory (DFT) and many-body perturbation theory (MBPT) approach to quantify the influence of defects on the electronic and optical properties of GaN. We predict, as expected, that introduction of a N or Ga vacancy results in several energetically favorable charged states within bulk GaN; these energetically favorable defects result in a significant modification of the quasiparticle and excitonic properties of GaN. We will discuss the implications of defect-induced-states for the electron transport and absorption properties of GaN. This work was partially supported by the Army Research Office (ARO) within the Collaborative Research Alliance (CRA-MSME).

  15. Saddle-like deformation in a dielectric elastomer actuator embedded with liquid-phase gallium-indium electrodes

    NASA Astrophysics Data System (ADS)

    Wissman, J.; Finkenauer, L.; Deseri, L.; Majidi, C.

    2014-10-01

    We introduce a dielectric elastomer actuator (DEA) composed of liquid-phase Gallium-Indium (GaIn) alloy electrodes embedded between layers of poly(dimethylsiloxane) (PDMS) and examine its mechanics using a specialized elastic shell theory. Residual stresses in the dielectric and sealing layers of PDMS cause the DEA to deform into a saddle-like geometry (Gaussian curvature K <0). Applying voltage Φ to the liquid metal electrodes induces electrostatic pressure (Maxwell stress) on the dielectric and relieves some of the residual stress. This reduces the longitudinal bending curvature and corresponding angle of deflection ϑ. Treating the elastomer as an incompressible, isotropic, NeoHookean solid, we develop a theory based on the principle of minimum potential energy to predict the principal curvatures as a function of Φ. Based on this theory, we predict a dependency of ϑ on Φ that is in strong agreement with experimental measurements performed on a GaIn-PDMS composite. By accurately modeling electromechanical coupling in a soft-matter DEA, this theory can inform improvements in design and fabrication.

  16. Saddle-like deformation in a dielectric elastomer actuator embedded with liquid-phase gallium-indium electrodes

    SciTech Connect

    Wissman, J.; Finkenauer, L.; Deseri, L.; Majidi, C.

    2014-10-14

    We introduce a dielectric elastomer actuator (DEA) composed of liquid-phase Gallium-Indium (GaIn) alloy electrodes embedded between layers of poly(dimethylsiloxane) (PDMS) and examine its mechanics using a specialized elastic shell theory. Residual stresses in the dielectric and sealing layers of PDMS cause the DEA to deform into a saddle-like geometry (Gaussian curvature K<0). Applying voltage Φ to the liquid metal electrodes induces electrostatic pressure (Maxwell stress) on the dielectric and relieves some of the residual stress. This reduces the longitudinal bending curvature and corresponding angle of deflection ϑ. Treating the elastomer as an incompressible, isotropic, NeoHookean solid, we develop a theory based on the principle of minimum potential energy to predict the principal curvatures as a function of Φ. Based on this theory, we predict a dependency of ϑ on Φ that is in strong agreement with experimental measurements performed on a GaIn-PDMS composite. By accurately modeling electromechanical coupling in a soft-matter DEA, this theory can inform improvements in design and fabrication.

  17. Alloy softening in binary molybdenum alloys

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.; Witzke, W. R.

    1972-01-01

    An investigation was conducted to determine the effects of alloy additions of Hf, Ta, W, Re, Os, Ir, and Pt on the hardness of Mo. Special emphasis was placed on alloy softening in these binary Mo alloys. Results showed that alloy softening was produced by those elements having an excess of s+d electrons compared to Mo, while those elements having an equal number or fewer s+d electrons than Mo failed to produce alloy softening. Alloy softening and hardening can be correlated with the difference in number of s+d electrons of the solute element and Mo.

  18. Composition of the core from gallium metal-silicate partitioning experiments

    NASA Astrophysics Data System (ADS)

    Blanchard, I.; Badro, J.; Siebert, J.; Ryerson, F. J.

    2015-10-01

    Gallium concentration (normalized to CI chondrites) in the mantle is at the same level as that of lithophile elements with similar volatility, implying that there must be little to no gallium in Earth's core. Metal-silicate partitioning experiments, however, have shown that gallium is a moderately siderophile element and should be therefore depleted in the mantle by core formation. Moreover, gallium concentrations in the mantle (4 ppm) are too high to be only brought by the late veneer; and neither pressure, nor temperature, nor silicate composition has a large enough effect on gallium partitioning to make it lithophile. We therefore systematically investigated the effect of core composition (light element content) on the partitioning of gallium by carrying out metal-silicate partitioning experiments in a piston-cylinder press at 2 GPa between 1673 K and 2073 K. Four light elements (Si, O, S, C) were considered, and their effect was found to be sufficiently strong to make gallium lithophile. The partitioning of gallium was then modeled and parameterized as a function of pressure, temperature, redox and core composition. A continuous core formation model was used to track the evolution of gallium partitioning during core formation, for various magma ocean depths, geotherms, core light element contents, and magma ocean composition (redox) during accretion. The only model for which the final gallium concentration in the silicate Earth matched the observed value is the one involving a light-element rich core equilibrating in a FeO-rich deep magma ocean (>1300 km) with a final pressure of at least 50 GPa. More specifically, the incorporation of S and C in the core provided successful models only for concentrations that lie far beyond their allowable cosmochemical or geophysical limits, whereas realistic O and Si amounts (less than 5 wt.%) in the core provided successful models for magma oceans deeper that 1300 km. These results offer a strong argument for an O- and Si-rich core, formed in a deep terrestrial magma ocean, along with oxidizing conditions.

  19. Antitumor efficacy and tolerability of systemically administered gallium acetylacetonate-loaded gelucire-stabilized nanoparticles.

    PubMed

    Wehrung, Daniel; Bi, Lipeng; Geldenhuys, Werner J; Oyewumi, Moses O

    2013-06-01

    The widespread clinical success with most gallium compounds in cancer therapy is markedly hampered by lack of tumor specific accumulation, poor tumor permeability and undesirable toxicity to healthy tissues. The aim of this work was to investigate for the first time antitumor mechanism of a new gallium compound (gallium acetylacetonate; GaAcAc) while assessing effectiveness of gelucire-stabilized nanoparticles (NPs) for potential application in gallium-based lung cancer therapy. NPs loaded with GaAcAc (Ga-NPs) were prepared using mixtures of cetyl alcohol with Gelucire 44/14 (Ga-NP-1) or Gelucire 53/13 (Ga-NP-2) as matrix materials. Of special note from this work is the direct evidence of involvement of microtubule disruption in antitumor effects of GaAcAc on human lung adenocarcinoma (A549). In-vivo tolerability studies were based on plasma ALT, creatinine levels and histopathological examination of tissues. The superior in-vivo antitumor efficacy of Ga-NPs over GaAcAc was depicted in marked reduction of tumor weight and tumor volume as well as histological assessment of excised tumors. Compared to free GaAcAc, Ga-NPs showed a 3-fold increase in tumor-to-blood gallium concentrations with minimized overall exposure to healthy tissues. Overall, enhancement of antitumor effects of GaAcAc by gelucire-stabilized NPs coupled with reduced exposure of healthy tissues to gallium would likely ensure desired therapeutic outcomes and safety of gallium-based cancer treatment. PMID:23858967

  20. Pulmonary gallium uptake in rats with granulomatosis induced by complete Freund adjuvant

    SciTech Connect

    Stanislas-Leguern, G.; Masse, R.; Jaubert, F.; Chretien, J.; Huchon, G.

    1988-01-01

    To investigate the mechanism of gallium-67 uptake in lung granulomatosis, we studied 13 rats in which lung granulomatosis was induced by injection of complete Freund adjuvant (CFA) and 14 controls. Gallium uptake was assessed in bronchoalveolar lavage fluid and lavaged lung. The cells responsible for gallium uptake were identified by latent image activation autoradiography. Gallium activity in both lavaged lungs and bronchoalveolar cells (BAC) was higher in CFA-treated animals than in controls (172,205 +/- 134,783 DPM versus 44,456 +/- 14,486 DPM +/- SD (p less than 0.05) and 40,083 +/- 16,350 DPM versus 9100 +/- 4114 DPM (p less than 0.05), respectively). In control rats, about two-thirds of total lung gallium was located in the interstitium, whereas in CFA-treated rats it was found in the mononuclear cells of lung granulomas. Gallium tracks were more numerous in the alveolar macrophages (AM) of CFA-treated rats than in control AM (28.4 +/- 10.0/field versus 8.4 +/- 3.8/field, p less than 0.001) but the number of tracks was proportional to the number of AM (52.4 +/- 18.7 versus 12.2 +/- 4.3, respectively; p less than 0.001). It is concluded that in rats with CFA-induced lung granulomatosis 1) pulmonary gallium uptake increases, 2) mononuclear cells are responsible for this uptake in both granulomas and AM, and 3) the increased uptake is due to the increased number of mononuclear cells.

  1. Gallium-containing phospho-silicate glasses: synthesis and in vitro bioactivity.

    PubMed

    Franchini, Mirco; Lusvardi, Gigliola; Malavasi, Gianluca; Menabue, Ledi

    2012-08-01

    A series of Ga-containing phospho-silicate glasses based on Bioglass 45S5, having molar formula 46.2SiO2·24.3Na2O·26.9CaO·2.6P2O5·xGa2O3 (x=1.0, 1.6, 3.5), were prepared by fusion method. The reference Bioglass 45S5 without gallium was also prepared. The synthesized glasses were immersed in simulated body fluid (SBF) for 30 days in order to observe ion release and hydroxyapatite (HA) formation. All Ga-containing glasses maintain the ability of HA formation as indicated by main X-ray diffractometric peaks and/or electronic scanning microscopy results. HA layer was formed after 1 day of SBF soaking in 45S5 glass containing up to 1.6% Ga2O3 content. Moreover, gallium released by the glasses was found to be partially precipitated on the glass surface as gallium phosphate. Further increase in gallium content reduced the ion release in SBF. The maximum of Ga(3+) concentration measured in solution is ~6 ppm determined for 3.5% Ga2O3 content. This amount is about half of the toxic level (14 ppm) of gallium and the glasses release gallium till 30 days of immersion in SBF. Considering the above results, the studied materials can be proposed as bioactive glasses with additional antimicrobial effect of gallium having no toxic outcome. PMID:24364938

  2. Investigating the effect of gallium curcumin and gallium diacetylcurcumin complexes on the structure, function and oxidative stability of the peroxidase enzyme and their anticancer and antibacterial activities.

    PubMed

    Jahangoshaei, Parisa; Hassani, Leila; Mohammadi, Fakhrossadat; Hamidi, Akram; Mohammadi, Khosro

    2015-10-01

    Curcumin has a wide spectrum of biological and pharmacological activities including anti-inflammatory, antioxidant, antiproliferative, antimicrobial and anticancer activities. Complexation of curcumin with metals has gained attention in recent years for improvement of its stability. In this study, the effect of gallium curcumin and gallium diacetylcurcumin on the structure, function and oxidative stability of horseradish peroxidase (HRP) enzyme were evaluated by spectroscopic techniques. In addition to the enzymatic investigation, the cytotoxic effect of the complexes was assessed on bladder, MCF-7 breast cancer and LNCaP prostate carcinoma cell lines by MTT assay. Furthermore, antibacterial activity of the complexes against S. aureus and E. coli was explored by dilution test method. The results showed that the complexes improve activity of HRP and also increase its tolerance against the oxidative condition. After addition of the complexes, affinity of HRP for hydrogen peroxide substrate decreases, while the affinity increases for phenol substrate. Circular dichroism, intrinsic and synchronous fluorescence spectra showed that the enzyme structure around the catalytic heme group becomes less compact and also the distance between the heme group and tryptophan residues increases due to binding of the complexes to HRP. On the whole, it can be concluded that the change in the enzyme structure upon binding to the gallium curcumin and gallium diacetylcurcumin complexes results in an increase in the antioxidant efficiency and activity of the peroxidise enzyme. The result of anticancer and antibacterial activities suggested that the complexes exhibit the potential for cancer treatment, but they have no significant antibacterial activity. PMID:26369539

  3. Gallium in Feldspar Minerals - an Underutilized Source of Petrogenetic Information

    NASA Astrophysics Data System (ADS)

    Renno, A. D.

    2007-12-01

    The trace element gallium is routinely analyzed in all kind of rocks. Regardless of this fact it is rarely used as a petrogenetic indicator element. Arguably the best known exception is the discrimination of A-type granites according to the Ga/Al value. Interpreting these data requires our understanding of how Ga is distributed between coexisting crystal phases and liquids. Because of the great importance of the feldspar minerals for the geochemical evolution of Ga a two- step method for Ga analysis of feldspar minerals using the electron microprobe was developed. The first step includes a screening for increased Ga-values during the routine feldspar analyses. A threshold of 100 ppm Ga was used to define 'Ga-rich feldspars'. These feldspars were analyzed for Ga using a special routine with optimized conditions for trace element analysis. To minimize the well known effects of diffusion of alkaline metals and to maintain the high spatial resolution an accelerating voltage of 15 kV was used. In order to improve precision and the lower detection limit long peak counting times of 360 - 600 seconds were chosen. The background curvature and possible interferences of both Ga-Kα and Ga-Lα lines were studied using standards very poor in gallium. The influence of the beam current on the stability of different feldspar types was tested. In order to ensure the integrity of the sample and the compliance of the analytical task an optimal ratio of beam current to beam diameter has to be chosen for every analysis. Using optimal conditions with low spatial resolution a lower detection limit of 33 ppm was reached. Using this two-step method we found unexpected high Ga values in feldspars of different rock types. Characteristic examples are albite with a Ga-Ca - ratio of > 1 from albite granites in the Central Eastern Desert (Egypt) and zoned plagioclase from mafic microgranular enclaves in granites formed by magma mixing (Karkonosze Mountains in Poland) with Ga-contents greater than 1000 ppm.

  4. Micro and nano-structured green gallium indium nitride/gallium nitride light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Stark, Christoph J. M.

    Light-emitting diodes (LEDs) are commonly designed and studied based on bulk material properties. In this thesis different approaches based on patterns in the nano and micrometer length scale range are used to tackle low efficiency in the green spectral region, which is known as “green gap”. Since light generation and extraction are governed by microscopic processes, it is instructive to study LEDs with lateral mesa sizes scaled to the nanometer range. Besides the well-known case of the quantum size effect along the growth direction, a continuous lateral scaling could reveal the mechanisms behind the purported absence of a green gap in nanowire LEDs and the role of their extraction enhancement. Furthermore the possibility to modulate strain and piezoelectric polarization by post growth patterning is of practical interest, because the internal electric fields in conventional wurtzite GaN LEDs cause performance problems. A possible alternative is cubic phase GaN, which is free of built-in polarization fields. LEDs on cubic GaN could show the link between strong polarization fields and efficiency roll-off at high current densities, also known as droop. An additional problem for all nitride-based LEDs is efficient light extraction. For a planar GaN LED only roughly 8% of the generated light can be extracted. Novel lightextraction structures with extraction-favoring geometry can yield significant increase in light output power. To investigate the effect of scaling the mesa dimension, micro and nano-sized LED arrays of variable structure size were fabricated. The nano-LEDs were patterned by electron beam lithography and dry etching. They contained up to 100 parallel nano-stripe LEDs connected to one common contact area. The mesa width was varied over 1 μm, 200 nm, and 50 nm. These LEDs were characterized electrically and optically, and the peak emission wavelength was found to depend on the lateral structure size. An electroluminescence (EL) wavelength shift of 3 nm towards smaller values was observed when the stripe width was reduced from 1 μm to 50 nm. At the same time a strong fourfold enhancement of the light emission from the patterned region over the unpatterned area was observed. Micro-patterned LEDs showed non-linear scaling of the light output power, and an enhancement of 39 % was achieved for structures with an area fill ratio of 0.5 over an LED with square mesa. Growth of cubic GaN and cubic GaInN/GaN LEDs was shown by M-OVPE in Vshaped grooves formed by the {111} planes of etched silicon. SEM images of the GaN layer in small ( 0.5 μm) regions show a contrast change where the phase boundary between cubic and wurtzite GaN is expected to occur. The growth parameter space is explored for optimal conditions while minimizing the alloying problem for GaN growth on Si. The cubic GaN phase is confirmed by electron back-scatter diffraction (EBSD) in the V-groove center, whereas wurtzite GaN is found near the groove edges. Luminescence of undoped GaN and GaInN/GaN multi-quantum well structures was studied by cathodoluminescence (CL). The undoped cubic GaN structure showed strong band-edge luminescence at 385 nm (3.22 eV) at 78 K, whereas for the MQW device strong emission at 498 nm is observed, even at room temperature. Full cubic LED structures were grown, and wavelength-stable electroluminescence at 489 nm was demonstrated. LEDs with integrated light extraction structures are grown on free-standing GaN substrates with different off-cut angles. The devices with different off-cut show pronounced features at the top surface that also penetrate the active region. For a 2.24° off-cut, these features resemble fish scales, where the feature sizes are in the μm-range. The 2.24° off-cut LED shows a 3.6-fold increased light output power compared to a LED on virtually on-axis substrate with 0.06° off-cut. The enhancement found in the fish scale LEDs is attributed to increased light scattering, effectively reducing the fraction of trapped light. These results show the potential of structures on the micro and nanometer scale for LED device performance and the progress on cubic GaN could open alternative ways to understand the droop problem.

  5. Selective etching of focused gallium ion beam implanted regions from silicon as a nanofabrication method

    NASA Astrophysics Data System (ADS)

    Han, Zhongmei; Vehkamäki, Marko; Mattinen, Miika; Salmi, Emma; Mizohata, Kenichiro; Leskelä, Markku; Ritala, Mikko

    2015-07-01

    A focused ion beam (FIB) is otherwise an efficient tool for nanofabrication of silicon structures but it suffers from the poor thermal stability of the milled surfaces caused by segregation of implanted gallium leading to severe surface roughening upon already slight annealing. In this paper we show that selective etching with KOH:H2O2 solutions removes the surface layer with high gallium concentration while blocking etching of the surrounding silicon and silicon below the implanted region. This remedies many of the issues associated with gallium FIB nanofabrication of silicon. After the gallium removal sub-nm surface roughness is retained even during annealing. As the etching step is self-limited to a depth of 25-30 nm for 30 keV ions, it is well suited for defining nanoscale features. In what is essentially a reversal of gallium resistless lithography, local implanted areas can be prepared and then subsequently etched away. Nanopore arrays and sub-100 nm trenches can be prepared this way. When protective oxide masks such as Al2O3 grown with atomic layer deposition are used together with FIB milling and KOH:H2O2 etching, ion-induced amorphization can be confined to sidewalls of milled trenches.

  6. (Polyfluoroaryl) fluoroanions of aluminum, gallium, and indium of enhanced utility, uses thereof, and products based thereon

    DOEpatents

    Marks, Tobin J.; Chen, You-Xian

    2001-01-01

    The (polyfluoroaryl)fluoroanions of aluminum, gallium, and indium are novel weakly coordinating anions which are highly fluorinated. (Polyfluoroaryl)fluoroanions of one such type contain at least one ring substituent other than fluorine. These (polyfluoroaryl)fluoroanions of aluminum, gallium, and indium have greater solubility in organic solvents, or have a coordinative ability essentially equal to or less than that of the corresponding (polyfluoroaryl)fluoroanion of aluminum, gallium, or indium in which the substituent is replaced by fluorine. Another type of new (polyfluoroaryl)fluoroanion of aluminum, gallium, and indium have 1-3 perfluorinated fused ring groups and 2-0 perfluorophenyl groups. When used as a cocatalyst in the formation of novel catalytic complexes with d- or f-block metal compounds having at least one leaving group such as a methyl group, these anions, because of their weak coordination to the metal center, do not interfere in the ethylene polymerization process, while affecting the propylene process favorably, if highly isotactic polypropylene is desired. Thus, the (polyfluoroaryl)fluoroanions of aluminum, gallium, and indium of this invention are useful in various polymerization processes such as are described.

  7. (Polyfluoroaryl) fluoroanions of aluminum, gallium, and indium of enhanced utility, uses thereof, and products based thereon

    DOEpatents

    Marks, Tobin J.; Chen, You-Xian

    2002-01-01

    The (polyfluoroaryl)fluoroanions of aluminum, gallium, and indium are novel weakly coordinating anions which are highly fluorinated. (Polyfluoroaryl)fluoroanions of one such type contain at least one ring substituent other than fluorine. These (polyfluoroaryl)fluoroanions of aluminum, gallium, and indium have greater solubility in organic solvents, or have a coordinative ability essentially equal to or less than that of the corresponding (polyfluoroaryl)fluoroanion of aluminum, gallium, or indium in which the substituent is replaced by fluorine. Another type of new (polyfluoroaryl)fluoroanion of aluminum, gallium, and indium have 1-3 perfluorinated fused ring groups and 2-0 perfluorophenyl groups. When used as a cocatalyst in the formation of novel catalytic complexes with d- or f-block metal compounds having at least one leaving group such as a methyl group, these anions, because of their weak coordination to the metal center, do not interfere in the ethylene polymerization process, while affecting the propylene process favorably, if highly isotactic polypropylene is desired. Thus, the (polyfluoroaryl)fluoroanions of aluminum, gallium, and indium of this invention are useful in various polymerization processes such as are described.

  8. Selective etching of focused gallium ion beam implanted regions from silicon as a nanofabrication method.

    PubMed

    Han, Zhongmei; Vehkamäki, Marko; Mattinen, Miika; Salmi, Emma; Mizohata, Kenichiro; Leskelä, Markku; Ritala, Mikko

    2015-07-01

    A focused ion beam (FIB) is otherwise an efficient tool for nanofabrication of silicon structures but it suffers from the poor thermal stability of the milled surfaces caused by segregation of implanted gallium leading to severe surface roughening upon already slight annealing. In this paper we show that selective etching with KOH:H2O2 solutions removes the surface layer with high gallium concentration while blocking etching of the surrounding silicon and silicon below the implanted region. This remedies many of the issues associated with gallium FIB nanofabrication of silicon. After the gallium removal sub-nm surface roughness is retained even during annealing. As the etching step is self-limited to a depth of 25-30 nm for 30 keV ions, it is well suited for defining nanoscale features. In what is essentially a reversal of gallium resistless lithography, local implanted areas can be prepared and then subsequently etched away. Nanopore arrays and sub-100 nm trenches can be prepared this way. When protective oxide masks such as Al2O3 grown with atomic layer deposition are used together with FIB milling and KOH:H2O2 etching, ion-induced amorphization can be confined to sidewalls of milled trenches. PMID:26062985

  9. Synthesis and Structural characterization of β-ketoiminate-stabilized gallium hydrides for chemical vapor deposition applications.

    PubMed

    Marchand, Peter; Pugh, David; Parkin, Ivan P; Carmalt, Claire J

    2014-08-11

    Bis-β-ketoimine ligands of the form [(CH2 )n {N(H)C(Me)CHC(Me)O}2 ] (L(n) H2 , n=2, 3 and 4) were employed in the formation of a range of gallium complexes [Ga(L(n) )X] (X=Cl, Me, H), which were characterised by NMR spectroscopy, mass spectrometry and single-crystal X-ray diffraction analysis. The β-ketoimine ligands have also been used for the stabilisation of rare gallium hydride species [Ga(L(n) )H] (n=2 (7); n=3 (8)), which have been structurally characterised for the first time, confirming the formation of five-coordinate, monomeric species. The stability of these hydrides has been probed through thermal analysis, revealing stability at temperatures in excess of 200 °C. The efficacy of all the gallium β-ketoiminate complexes as molecular precursors for the deposition of gallium oxide thin films by chemical vapour deposition (CVD) has been investigated through thermogravimetric analysis and deposition studies, with the best results being found for a bimetallic gallium methyl complex [L(3) {GaMe2 }2 ] (5) and the hydride [Ga(L(3) )H] (8). The resulting films (F5 and F8, respectively) were amorphous as-deposited and thus were characterised primarily by XPS, EDXA and SEM techniques, which showed the formation of stoichiometric (F5) and oxygen-deficient (F8) Ga2 O3 thin films. PMID:25043194

  10. Cleansing the colon in gallium-67 scintigraphy: a prospective comparison of regimens

    SciTech Connect

    Novetsky, G.J.; Turner, D.A.; Ali, A.; Raynor, W.J.; Fordham, E.W.

    1981-11-01

    Colonic accumulation of gallium-67 frequently complicates the interpretation of gallium-67 scintigrams. Although various modes of cleansing the colon prior to scintigraphy have been suggested, there is controversy over their efficacy and none have been tested prospectively. Three hundred nine patients undergoing gallium-67 scintigraphy were randomly assigned to one of four cleansing regimens: (1) a high fiber diet (78 patients); (2) castor oil (76); (3) milk of magnesia and cascara (76); and (4) no preparation (79). Patient compliance rates for the four regimens were 17%, 32%, 36%, and 46%, respectively. After noncompliant patients were excluded, gallium-67 scintigrams were graded for colonic activity on a scale of 0-3 by three independent, experienced observers. Gallium-67 activity in the colon was significantly less after adminstration of castor oil than after no prepartion (p = 0.083). Regimen 3 did not produce significantly better results than regimen 4 (p = 0.42). A major impediment to the success of any cleansing regimen seems to be poor compliance of patients.

  11. Cleansing the colon in gallium-67 scintigraphy: a prospective comparison of regimens

    SciTech Connect

    Novetsky, G.J.; Turner, D.A.; Ali, A.; Raynor, W.J. Jr.; Fordham, E.W.

    1981-01-01

    Colonic accumulation of gallium-67 frequently complicates the interpretation of gallium-67 scintigrams. Although various modes of cleansing the colon prior to scintigraphy have been suggested, there is controversy over their efficacy and none have been tested prospectively. Three hundred nine patients undergoing gallium-67 scintigraphy were randomly assigned to one of four cleansing regimens: (1) a high fiber diet (78 patients); (2) castor oil (76); (3) milk of magnesia and cascara (76); and (4) not preparation (79). Patient compliance rates for the four regimens were 17%, 32%, 36%, and 46%, respectively. After noncompliant patients were excluded, gallium-67 scintigrams were graded for colonic activity on a scale of 0-3 by three independent, experienced observers. Gallium-67 activity in the colon was significantly less after administration of castor oil than after no preparation (p . 0.047). A high fiber diet also resulted in a substantial reduction of colonic activity when compared with no preparation; the difference, however, was not statistically significant (p . 0.083). Regimen 3 did not produce significantly better results than regimen 4 (p . 0.42). A major impediment to the success of any cleansing regimen seems to be poor compliance of patients.

  12. Biofilm formation on titanium implants counteracted by grafting gallium and silver ions.

    PubMed

    Cochis, Andrea; Azzimonti, Barbara; Della Valle, Cinzia; Chiesa, Roberto; Arciola, Carla Renata; Rimondini, Lia

    2015-03-01

    Biofilm-associated infections remain the leading cause of implant failure. Thanks to its established biocompatibility and biomechanical properties, titanium has become one of the most widely used materials for bone implants. Engineered surface modifications of titanium able to thwart biofilm formation while endowing a safe anchorage to eukaryotic cells are being progressively developed. Here surfaces of disks of commercial grade 2 titanium for bone implant were grafted with gallium and silver ions by anodic spark deposition. Scanning electron microscopy of the surface morphology and energy dispersive X-ray spectroscopy were used for characterization. Gallium-grafted titanium was evaluated in comparison with silver-grafted titanium for both in vivo and in vitro antibiofilm properties and for in vitro compatibility with human primary gingival fibroblasts. Surface-modified materials showed: (i) homogeneous porous morphology, with pores of micrometric size; (ii) absence of cytotoxic effects; (iii) ability to support in vitro the adhesion and spreading of gingival fibroblasts; and (iv) antibiofilm properties. Although both silver and gallium exhibited in vitro strong antibacterial properties, in vivo gallium was significantly more effective than silver in reducing number and viability of biofilm bacteria colonies. Gallium-based treatments represent promising titanium antibiofilm coatings to develop new bone implantable devices for oral, maxillofacial, and orthopedic applications. PMID:25044610

  13. The global anthropogenic gallium system: determinants of demand, supply and efficiency improvements.

    PubMed

    Løvik, Amund N; Restrepo, Eliette; Müller, Daniel B

    2015-05-01

    Gallium has been labeled as a critical metal due to rapidly growing consumption, importance for low-carbon technologies such as solid state lighting and photovoltaics, and being produced only as a byproduct of other metals (mainly aluminum). The global system of primary production, manufacturing, use and recycling has not yet been described or quantified in the literature. This prevents predictions of future demand, supply and possibilities for efficiency improvements on a system level. We present a description of the global anthropogenic gallium system and quantify the system using a combination of statistical data and technical parameters. We estimated that gallium was produced from 8 to 21% of alumina plants in 2011. The most important applications of gallium are NdFeB permanent magnets, integrated circuits and GaAs/GaP-based light-emitting diodes, demanding 22-37%, 16-27%, and 11-21% of primary metal production, respectively. GaN-based light-emitting diodes and photovoltaics are less important, both with 2-6%. We estimated that 120-170 tons, corresponding to 40-60% of primary production, ended up in production wastes that were either disposed of or stored. While demand for gallium is expected to rise in the future, our results indicated that it is possible to increase primary production substantially with conventional technology, as well as improve the system-wide material efficiency. PMID:25884251

  14. Hydrogenation of palladium rich compounds of aluminium, gallium and indium

    SciTech Connect

    Kohlmann, H.

    2010-02-15

    Palladium rich intermetallic compounds of aluminium, gallium and indium have been studied before and after hydrogenation by powder X-ray diffraction and during hydrogenation by in situ thermal analysis (DSC) at hydrogen gas pressures up to 39 MPa and temperatures up to 700 K. Very weak DSC signals and small unit cell increases of below 1% for AlPd{sub 2}, AlPd{sub 3}, GaPd{sub 2}, Ga{sub 5}Pd{sub 13}, In{sub 3}Pd{sub 5}, and InPd{sub 2} suggest negligible hydrogen uptake. In contrast, for both tetragonal modifications of InPd{sub 3} (ZrAl{sub 3} and TiAl{sub 3} type), heating to 523 K at 2 MPa hydrogen pressure leads to a rearrangement of the intermetallic structure to a cubic AuCu{sub 3} type with an increase in unit cell volume per formula unit by 3.6-3.9%. Gravimetric analysis suggests a composition InPd{sub 3}H{sub a}pprox{sub 0.8} for the hydrogenation product. Very similar behaviour is found for the deuteration of InPd{sub 3}. - Graphical abstract: In situ differential scanning calorimetry of the hydrogenation of tetragonal InPd{sub 3} (ZrAl{sub 3} type) at 1.3 MPa hydrogen pressure.

  15. Nanostructured gallium nitride powder functionalized with a fluorophore terminated peptide

    NASA Astrophysics Data System (ADS)

    Berg, Nora; Ivanisevic, Albena

    2015-09-01

    Nanostructured gallium nitride (GaN) powder was functionalized with a biomolecule terminated with a fluorophore. The fluorophore was used to enhance and modulate the luminescent properties of the semiconductor powder. A simple two-step wet-chemistry in situ modification approach resulted in covalent attachment of the peptide to the powder. X-ray photoelectron spectroscopy survey data confirmed qualitatively that the peptide molecules were successfully attached to the surface of the powder with the presence of a phosphorus peak as well as an increase in nitrogen atomic percentage on the surface of the material. The bonding and stability of the modification to the nanostructured surface was assessed by quantitatively analyzing high-resolution regional scans. Photoluminescence Spectroscopy mapped changes to the optical properties of the powder upon dye terminated peptide attachment. A clear shift in the luminescence peak was recorded after the powder was functionalized. The results demonstrate a straight-forward way to alter the emission characteristics of a nanostructured semiconductor material. The role of material defects on the powder surface is used to explain the initial and altered luminescence properties.

  16. Gallium arsenide pilot line for high performance components

    NASA Astrophysics Data System (ADS)

    1990-01-01

    The Gallium Arsenide Pilot Line for High Performance Components (Pilot Line III) is to develop a facility for the fabrication of GaAs logic and memory chips. The first thirty months of this contract are now complete, and this report covers the period from March 27 through September 24, 1989. Similar to the PT-2M SRAM function for memories, the six logic circuits of PT-2L and PT-2M have served their functions as stepping stones toward the custom, standard cell, and cell array logic circuits. All but one of these circuits was right first time; the remaining circuit had a layout error due to a bug in the design rule checker that has since been fixed. The working devices all function over the full temperature range from -55 to 125 C. They all comfortably meet the 200 MHz requirement. They do not solidly conform to the required input and output voltage levels, particularly Vih. It is known that these circuits were designed with the older design models and that they came from an era where the DFET thresholds were often not on target.

  17. Gate modulation of anodically etched gallium arsenide nanowire random network

    NASA Astrophysics Data System (ADS)

    Aikawa, Shinya; Yamada, Kohei; Asoh, Hidetaka; Ono, Sachiko

    2016-06-01

    Gallium arsenide nanowires (GaAs NWs) formed by anodic etching show an electrically semi-insulating behavior because of charge carrier depletion caused by high interface state density. Here, we demonstrate the gate modulation of an anodically etched GaAs NW random network. By applying a reverse bias voltage after anodic etching of bulk GaAs, hydrogen ion exposure of the depleted NW region occurs, and then the interface state density is possibly decreased owing to the reduction in the amount of excess As generated at the interface between the amorphous Ga2O3 and GaAs layers. Consequently, the drain current of the thin-film transistor (TFT) with the GaAs NW random network was increased and was changed by the gate voltage. In contrast, the random network film remained in the insulator in the absence of reverse electrolysis treatment. The TFT performance is still insufficient but may be improved by optimizing the hydrogen ion exposure conditions.

  18. Size-dependent pyroelectric properties of gallium nitride nanowires

    NASA Astrophysics Data System (ADS)

    Zhang, Jin; Wang, Chengyuan

    2016-04-01

    The size scale effect on the pyroelectric properties is studied for gallium nitride (GaN) nanowires (NWs) based on molecular dynamics simulations and the theoretical analysis. Due to the significant influence of the surface thermoelasticity and piezoelectricity at the nanoscale, the pyroelectric coefficient of GaN NWs is found to depend on the cross-sectional size. This size-dependent pyroelectric coefficient of GaN NWs together with the size-dependent dielectric constant reported in our previous study is employed to study the pyroelectric potential of GaN NWs subjected to heating. The results show that the size scale effect is significant for thin NWs (cross-sectional size in nanometers) and may raise the pyroelectric potential of GaN NWs by over 10 times. Such a size scale effect on the pyroelectric properties of NWs originates from the influence of thermoelasticity, piezoelectricity, and dielectricity at the nanoscale and decreases with increasing cross-section of GaN NWs. It is expected that the present study may have strong implication in the field of energy harvesting at the nanoscale, as pyroelectricity offers a new avenue to the design of novel nanogenerators.

  19. Ion beam deposition of epitaxial germanium and gallium arsenide layers

    NASA Astrophysics Data System (ADS)

    Haynes, T. E.

    1989-07-01

    The traveler presented an invited paper entitled, Ion Beam Deposition of Epitaxial Germanium and Gallium Arsenide Layers, at the Twelfth Symposium on Ion Sources and Ion-Assisted Technology (ISIAT '89) in Tokyo. During informal conversations at this meeting, the traveler was informed about a new Japanese initiative, sponsored by the Ministry of International Trade and Industry and an industrial consortium, to establish an Ion Engineering Research Center, whose purpose will be to provide sophisticated equipment and technology base for exploring and developing new applications of ion beam processing. The traveler also visited five Japanese laboratories involved in research on ion-solid interactions. Developments in ionized cluster beam (ICB) deposition were emphasized at ISIAT '89 and during visits to Kyoto University, where the ICB technique was pioneered, and to Mitsubishi Electric's Itami Works, where commercial ICB systems are now being produced. Discussions at Osaka University concentrated on the application of focused ion beams for maskless patterning of submicron devices and on recent studies of one-dimensional quantum effects in semiconductor wires. At Hitachi Research Laboratory, basic research on thin-film growth was described, as well as progress toward the development of a variable frequency RF quadrupole accelerator for ion implantation.

  20. Liquid gallium columns sheathed with carbon: Bulk synthesis and manipulation.

    PubMed

    Zhan, Jinhua; Bando, Yoshio; Hu, Junqing; Golberg, Dmitri; Nakanishi, Haruyuki

    2005-06-16

    It is impossible to fabricate isolated gallium nanomaterials due to the low melting point of Ga (29.8 degrees C) and its high reactivity. We report the bulk synthesis of uniform liquid Ga columns encapsulated into carbon nanotubes through high-temperature chemical reaction between Ga and CH4. The diameter of filled Ga liquid columns is approximately 25 nm, and their length is up to several micrometers. The thickness of the carbon sheaths is approximately 6 nm. Simultaneous condensation of a Ga vapor and carbon clusters results in the generation of Ga-filled carbon nanotubes. A convergent 300 kV electron beam generated in a field emission high-resolution electron microscope is demonstrated to be a powerful tool for delicate manipulation of the liquid Ga nanocolumns: they can be gently joined, cut, and sealed within carbon nanotubes. The self-organization of a carbon sheath during the electron-beam irradiation is discussed. The electron-beam irradiation may also become a decent tool for Ga-filled carbon nanotube thermometer calibration. PMID:16852421

  1. Packaging of an iron-gallium (Galfenol) nanowire acoustic sensor

    NASA Astrophysics Data System (ADS)

    Jain, Rupal; McCluskey, F. Patrick; Flatau, Alison B.; Stadler, Bethanie J. H.

    2007-04-01

    Packaging is a key issue for the effective working of an iron-gallium (Galfenol) nanowire acoustic sensor for underwater applications. The nanowire acoustic sensor incorporates cilia-like nanowires made of galfenol, a magnetostrictive material, which responds by changing magnetic flux flowing through it due to bending stress induced by the incoming acoustic waves. This stress induced change in the magnetic flux density is detected by a GMR sensor. An effective package should provide a suitably protective environment to these nanowires, while allowing sound waves to reach the nanowires with a minimum level of attenuation. A bio-inspired MEMS package has been designed, analogous to a human-ear cochlea for the nanowire acoustic sensor. In this paper, the process sequence for fabrication of the package is presented. Unlike other microphones, the nanoacoustic sensor has been enclosed in a cavity to allow free movement of the nanowires in a fluid medium. The package also ensures resisting ingression of sea water and salt ions to prevent the corrosion of sensor components. The effect of package material on sensor performance was investigated by conducting experiments on acoustic impedance and attenuation characteristics, and salt water absorption properties. The package filled with silicone oil and molded with polydimethylsiloxane (PDMS) is observed to outperform other packages at all frequencies by minimizing attenuation of the acoustic waves.

  2. Spin-phonon coupling in scandium doped gallium ferrite

    SciTech Connect

    Chakraborty, Keka R. E-mail: smyusuf@barc.gov.in; Mukadam, M. D.; Basu, S.; Yusuf, S. M. E-mail: smyusuf@barc.gov.in; Paul, Barnita; Roy, Anushree; Grover, Vinita; Tyagi, A. K.

    2015-03-28

    We embarked on a study of Scandium (Sc) doped (onto Ga site) gallium ferrite (GaFeO{sub 3}) and found remarkable magnetic properties. In both doped as well as parent compounds, there were three types of Fe{sup 3+} ions (depending on the symmetry) with the structure conforming to space group Pna2{sub 1} (Sp. Grp. No. 33) below room temperature down to 5 K. We also found that all Fe{sup 3+} ions occupy octahedral sites, and carry high spin moment. For the higher Sc substituted sample (Ga{sub 1−x}Sc{sub x}FeO{sub 3}: x = 0.3), a canted magnetic ordered state is found. Spin-phonon coupling below Néel temperature was observed in doped compounds. Our results indicated that Sc doping in octahedral site modifies spin-phonon interactions of the parent compound. The spin-phonon coupling strength was estimated for the first time in these Sc substituted compounds.

  3. Enhanced photothermal conversion in vertically oriented gallium arsenide nanowire arrays.

    PubMed

    Walia, Jaspreet; Dhindsa, Navneet; Flannery, Jeremy; Khodabad, Iman; Forrest, James; LaPierre, Ray; Saini, Simarjeet S

    2014-10-01

    The photothermal properties of vertically etched gallium arsenide nanowire arrays are examined using Raman spectroscopy. The nanowires are arranged in square lattices with a constant pitch of 400 nm and diameters ranging from 50 to 155 nm. The arrays were illuminated using a 532 nm laser with an incident energy density of 10 W/mm(2). Nanowire temperatures were highly dependent on the nanowire diameter and were determined by measuring the spectral red-shift for both TO and LO phonons. The highest temperatures were observed for 95 nm diameter nanowires, whose top facets and sidewalls heated up to 600 and 440 K, respectively, and decreased significantly for the smaller or larger diameters studied. The diameter-dependent heating is explained by resonant coupling of the incident laser light into optical modes of the nanowires, resulting in increased absorption. Photothermal activity in a given nanowire diameter can be optimized by proper wavelength selection, as confirmed using computer simulations. This demonstrates that the photothermal properties of GaAs nanowires can be enhanced and tuned by using a photonic lattice structure and that smaller nanowire diameters are not necessarily better to achieve efficient photothermal conversion. The diameter and wavelength dependence of the optical coupling could allow for localized temperature gradients by creating arrays which consist of different diameters. PMID:25233265

  4. Investigation of a Gallium MPD Thruster with an Ablating Cathode

    NASA Technical Reports Server (NTRS)

    Thomas, Robert E.; Burton, Rodney L.; Polzin, Kurt A.

    2010-01-01

    Arc impedance, exhaust velocity, and plasma probe measurements are presented. The thruster is driven by a 50 microsecond pulse from a 6.2 milliohm pulse forming network, and gallium is supplied to the discharge by evaporation of the cathode. The arc voltage is found to vary linearly with the discharge current with an arc impedance of 6.5 milliohms. Electrostatic probes yield an exhaust velocity that is invariant with the discharge current and has a peak value of 20 kilometers per second, which is in reasonable agreement with the value (16 plus or minus 1 kilometer per second) calculated from the mass bit and discharge current data. Triple probe measurements yield on axis electron temperatures in the range of 0.8-3.8 eV, electron densities in the range of 1.6 x 10(exp 21) to 2.1 x 10(exp 22) per cubic meter, and a divergence half angle of 16 degrees. Measurements within the interelectrode region yield a peak magnetic field of 0.8 T, and the observed radial trends are consistent with an azimuthally symmetric current distribution. A cathode power balance model is coupled with an ablative heat conduction model predicting mass bit values that are within 20% of the experimental values.

  5. Unusually low thermal conductivity of gallium nitride nanowires

    NASA Astrophysics Data System (ADS)

    Guthy, Csaba; Nam, Chang-Yong; Fischer, John E.

    2008-03-01

    We report measurements of thermal conductivity κ on individual gallium nitride nanowires (GaN NWs) with diameters ranging from 97to181nm grown by thermal chemical vapor deposition. We observed unexpectedly small κ values, in the range of 13-19W/mK at 300K, with very weak diameter dependence. We also observe unusual power law κ ˜Tn behavior with n =1.8 at low temperature. Electron-energy-loss-spectroscopy measurements indicate Si and O concentrations in the ranges of 0.1-1 and 0.01-0.1at.%, respectively. Based on extensive numerical calculations, we conclude that both the unexpectedly low κ and the T1.8 dependence are caused by unusually large mass-difference scattering, primarily from Si impurities. Our analysis also suggests that mass-difference scattering rates are significantly enhanced by the reduced phonon group velocity in nanoscale systems. Planar defects running the length of the NW, previously characterized in detail, may also play a role in limiting the phonon mean free path.

  6. Gallium arsenide deep-level optical emitter for fibre optics.

    PubMed

    Pan, Janet L; McManis, Joseph E; Osadchy, Thomas; Grober, Louise; Woodall, Jerry M; Kindlmann, Peter J

    2003-06-01

    Fibre-optic components fabricated on the same substrate as integrated circuits are important for future high-speed communications. One industry response has been the costly push to develop indium phosphide (InP) electronics. However, for fabrication simplicity, reliability and cost, gallium arsenide (GaAs) remains the established technology for integrated optoelectronics. Unfortunately, the GaAs bandgap wavelength (0.85 microm) is far too short for fibre optics at 1.3-1.5 microm. This has led to work on materials that have a large lattice mismatch on GaAs. Here we demonstrate the first light-emitting diode (LED) that emits at 1.5 microm fibre-optic wavelengths in GaAs using optical transitions from arsenic antisite (As(Ga)) deep levels. This is an enabling technology for fibre-optic components that are lattice-matched to GaAs integrated circuits. We present experimental results showing significant internal optical power (24 mW) and speed (in terahertz) from GaAs optical emitters using deep-level transitions. Finally, we present theory showing the ultimate limit to the efficiency-bandwidth product of semiconductor deep-level optical emitters. PMID:12738958

  7. Gallium in the Carlin-type gold deposits

    SciTech Connect

    Owens, P.A.; Ikramuddin, M.

    1985-01-01

    Gallium and aluminum are dispersed elements and are associated with each other because of their similar geochemical characteristics. The somewhat larger size of the Ga ion suggests that it may concentrate in residual melts and hydrothermal solutions. Ga and Al are also presumed to have different mobilities at a pH range of 3.4-4.1 and in alkaline solutions. Very little precise and accurate data exist on the concentration of Ga in hydrothermally altered rocks. In order to understand the behavior of Ga during hydrothermal processes and to explore the possibility of utilizing Ga as a guide to mineral deposits, unmineralized and mineralized rocks from four Carlin-type gold deposits were studied. Ga was analyzed by a newly developed precise and accurate method by electrothermal atomic absorption spectrophotometry. The Carlin-type gold deposits studied include Carlin and Alligator Ridge deposits of Nevada, Mercur deposit of Utah, and north Moccasin deposits of Montana. In all the mineralized areas there is more Ga in hydrothermally altered (mineralized) rocks than in unaltered (unmineralized) rocks. The enrichment factors for Ga differ from deposit to deposit. The highest enrichment of Ga is found in the north Moccasin deposits, where the average values in unmineralized and mineralized rocks are about 2 ppm and 10 ppm respectively. The oxidized mineralized rocks of the Carlin-type gold deposits have higher contents of Ga than carbonaceous rocks, while siliceous rocks contain the lowest Ga concentrations.

  8. Low-temperature thermal conductivity of terbium-gallium garnet

    SciTech Connect

    Inyushkin, A. V. Taldenkov, A. N.

    2010-11-15

    Thermal conductivity of paramagnetic Tb{sub 3}Ga{sub 5}O{sub 12} (TbGG) terbium-gallium garnet single crystals is investigated at temperatures from 0.4 to 300 K in magnetic fields up to 3.25 T. A minimum is observed in the temperature dependence {kappa}(T) of thermal conductivity at T{sub min} = 0.52 K. This and other singularities on the {kappa}(T) dependence are associated with scattering of phonons from terbium ions. The thermal conductivity at T = 5.1 K strongly depends on the magnetic field direction relative to the crystallographic axes of the crystal. Experimental data are considered using the Debye theory of thermal conductivity taking into account resonance scattering of phonons from Tb{sup 3+} ions. Analysis of the temperature and field dependences of the thermal conductivity indicates the existence of a strong spin-phonon interaction in TbGG. The low-temperature behavior of the thermal conductivity (field and angular dependences) is mainly determined by resonance scattering of phonons at the first quasi-doublet of the electron spectrum of Tb{sup 3+} ion.

  9. Epitaxial Zinc Oxide Semiconductor Film deposited on Gallium Nitride Substrate

    NASA Astrophysics Data System (ADS)

    McMaster, Michael; Oder, Tom

    2011-04-01

    Zinc oxide (ZnO) is a wide bandgap semiconductor which is very promising for making efficient electronic and optical devices. The goal of this research was to produce high quality ZnO film on gallium nitride (GaN) substrate by optimizing the substrate temperature. The GaN substrates were chemically cleaned and mounted on a ceramic heater and loaded into a vacuum deposition chamber that was pumped down to a base pressure of 3 x 10-7 Torr. The film deposition was preceded by a 30 minute thermal desorption carried in vacuum at 500 ^oC. The ZnO thin film was then sputter-deposited using an O2/Ar gas mixture onto GaN substrates heated at temperatures varying from 20 ^oC to 500 ^oC. Post-deposition annealing was done in a rapid thermal processor at 900 ^oC for 5 min in an ultrapure N2 ambient to improve the crystal quality of the films. The films were then optically characterized using photoluminescence (PL) measurement with a UV laser excitation. Our measurements reveal that ZnO films deposited on GaN substrate held at 200 ^oC gave the best film with the highest luminous intensity, with a peak energy of 3.28 eV and a full width half maximum of 87.4 nm. Results from low temperature (10 K) PL measurements and from x-ray diffraction will also be presented.

  10. Technical and economic issues for gallium antimonide based thermophotovoltaic systems

    NASA Astrophysics Data System (ADS)

    Gruenbaum, P. E.; Kuryla, M. S.; Sundaram, V. S.

    1995-01-01

    Most of the research in thermophotovoltaic systems to date has involved silicon cells as the photovoltaic converter. Recent developments in gallium antimonide (GaSb) cells create an alternative device which offers similar high efficiencies (exceeding 25%) at much lower emitter temperatures (1600 °C for GaSb vs 2300 °C for Si). System level concerns are more easily (less expensively) managed at lower emitter temperatures; however, the photon flux density at the cell diminishes exponentially with temperature. The cells' power density (W/cm2) diminishes as the emitter temperature is reduced, raising the system power cost (/W) for a fixed cell cost (/cm2). A comparison of the cell component of power cost is made for thermophotovoltaic systems using GaSb and silicon cells over a range of emitter temperatures. Cost estimates are made for GaSb and silicon cells, using the burdened costs of silicon foundries for various semiconductor processing steps. These calculations indicate that GaSb cell cost per watt is lower for low emitter temperatures, and that silicon cell cost per watt is lower for high emitter temperatures. The cell component costs are roughly equal at 1500 °C, at an estimated cost of 400/kW.

  11. Metal alloy identifier

    DOEpatents

    Riley, William D.; Brown, Jr., Robert D.

    1987-01-01

    To identify the composition of a metal alloy, sparks generated from the alloy are optically observed and spectrographically analyzed. The spectrographic data, in the form of a full-spectrum plot of intensity versus wavelength, provide the "signature" of the metal alloy. This signature can be compared with similar plots for alloys of known composition to establish the unknown composition by a positive match with a known alloy. An alternative method is to form intensity ratios for pairs of predetermined wavelengths within the observed spectrum and to then compare the values of such ratios with similar values for known alloy compositions, thereby to positively identify the unknown alloy composition.

  12. Ohmic contact formation process on low n-type gallium arsenide (GaAs) using indium gallium zinc oxide (IGZO)

    SciTech Connect

    Yang, Seong-Uk; Jung, Woo-Shik; Lee, In-Yeal; Jung, Hyun-Wook; Kim, Gil-Ho; Park, Jin-Hong

    2014-02-01

    Highlights: • We propose a method to fabricate non-gold Ohmic contact on low n-type GaAs with IGZO. • 0.15 A/cm{sup 2} on-current and 1.5 on/off-current ratio are achieved in the junction. • InAs and InGaAs formed by this process decrease an electron barrier height. • Traps generated by diffused O atoms also induce a trap-assisted tunneling phenomenon. - Abstract: Here, an excellent non-gold Ohmic contact on low n-type GaAs is demonstrated by using indium gallium zinc oxide and investigating through time of flight-secondary ion mass spectrometry, X-ray photoelectron spectroscopy, transmission electron microscopy, J–V measurement, and H [enthalpy], S [entropy], Cp [heat capacity] chemistry simulation. In is diffused through GaAs during annealing and reacts with As, forming InAs and InGaAs phases with lower energy bandgap. As a result, it decreases the electron barrier height, eventually increasing the reverse current. In addition, traps generated by diffused O atoms induce a trap-assisted tunneling phenomenon, increasing generation current and subsequently the reverse current. Therefore, an excellent Ohmic contact with 0.15 A/cm{sup 2} on-current density and 1.5 on/off-current ratio is achieved on n-type GaAs.

  13. The comparison between gallium arsenide and indium gallium arsenide as materials for solar cell performance using Silvaco application

    SciTech Connect

    Zahari, Suhaila Mohd; Norizan, Mohd Natashah; Mohamad, Ili Salwani; Osman, Rozana Aina Maulat; Taking, Sanna

    2015-05-15

    The work presented in this paper is about the development of single and multilayer solar cells using GaAs and InGaAs in AM1.5 condition. The study includes the modeling structure and simulation of the device using Silvaco applications. The performance in term of efficiency of Indium Gallium Arsenide (InGaAs) and GaAs material was studied by modification of the doping concentration and thickness of material in solar cells. The efficiency of the GaAs solar cell was higher than InGaAs solar cell for single layer solar cell. Single layer GaAs achieved an efficiency about 25% compared to InGaAs which is only 2.65% of efficiency. For multilayer which includes both GaAs and InGaAs, the output power, P{sub max} was 8.91nW/cm² with the efficiency only 8.51%. GaAs is one of the best materials to be used in solar cell as a based compared to InGaAs.

  14. Novel ethylenediamine-gallium phosphate containing 6-fold coordinated gallium atoms with unusual four equatorial Ga-N bonds

    NASA Astrophysics Data System (ADS)

    Torre-Fernández, Laura; Espina, Aránzazu; Khainakov, Sergei A.; Amghouz, Zakariae; García, José R.; García-Granda, Santiago

    2014-07-01

    A novel ethylenediamine-gallium phosphate, formulated as Ga(H2NCH2CH2NH2)2PO4·2H2O, was synthesized under hydrothermal conditions. The crystal structure, including hydrogen positions, was determined using single-crystal X-ray diffraction data (monoclinic, a=9.4886(3) Å, b=6.0374(2) Å, c=10.2874(3) Å, and β=104.226(3)°, space group Pc) and the bulk was characterized by chemical (Ga-P-C-H-N) and thermal analysis (TG-MS and DSC), including activation energy data of its thermo-oxidative degradation, powder X-ray diffraction (PXRD), solid-state nuclear magnetic resonance (SS-NMR) measurements, and transmission electron microscopy (TEM, SAED/NBD, and STEM BF-EDX). The crystal structure is built up of infinite zig-zag chains running along the c-axis, formed by vertex-shared {PO4} and {GaO2N4} polyhedra. The new compound is characterized by unusual four equatorial Ga-N bonds coming from two nonequivalent ethylenediamine molecules and exhibits strong blue emission at 430 nm (λex=350 nm) in the solid state at room temperature.

  15. Total neutron scattering investigation of the structure of a cobalt gallium oxide spinel prepared by solvothermal oxidation of gallium metal

    NASA Astrophysics Data System (ADS)

    Playford, Helen Y.; Hannon, Alex C.; Tucker, Matthew G.; Lees, Martin R.; Walton, Richard I.

    2013-11-01

    A new solvothermal synthesis route to mixed-metal gallium oxides with the spinel structure has been developed for ternary oxides of ideal composition Ga3-xMxO4-y (M=Co, Zn, Ni). The structure of the novel cobalt gallate produced in this manner, Ga1.767(8)Co0.973(8)O3.752(8), has been determined from total neutron scattering to be a partially defective spinel with mixed-valent cobalt (approximately 25% Co3+ and 75% Co2+) and with vacancies on approximately 6% of oxygen sites. Pair distribution function (PDF) analysis reveals significant local deviations from the average cubic structure, which are attributed to the conflicting coordination preferences of the Co2+ (potential Jahn-Teller distortion) and Ga3+ (Ga off-centring). Reverse Monte Carlo (RMC) modelling supports this conclusion since different metal-oxygen bond-distance distributions are found for the two cations in the refined configuration. An investigation of magnetic properties shows evidence of short-range magnetic order and spin-glass-like behaviour, consistent with the structural disorder of the material.

  16. Renal gallium accumulation in rats with antibiotic-induced nephritis: clinical implications. Concise communication

    SciTech Connect

    Taylor, A.; Nelson, H.; Vasquez, M.; Hollenbeck, J.

    1980-07-01

    To determine the effect of antibiotic-induced nephrotoxicity on the renal accumulation of gallium, groups of ten Sprague-Dawley rats were given intraperitoneal injections of gentamycin, amphotericin, or neomycin for a period of 16 to 21 days. In all cases, mild to moderate nephrotoxicity was documented by one or more of the following parameters: serum creatinine, renal weight, urine volume (renal concentrating ability), light microscopy, and electron microscopy. In none of these cases was the renal accumulation of gallium increased over control values. Consequently, diffuse renal accumulation of gallium in patients with subclinical or mild nephrotoxicity is unlikely to be related to short-term treatment with aminoglycosides or amphotericin. In such cases, the physician should seek some other clinical explanation, such as infection.

  17. Gallium scanning in differentiating malignant from benign asbestos-related pleural disease

    SciTech Connect

    Teirstein, A.S.; Chahinian, P.; Goldsmith, S.J.; Sorek, M.

    1986-01-01

    In order to assess the utility of 67gallium citrate in delineating malignant pleural mesothelioma from benign asbestos-related pleural disease, 49 patients with malignant mesothelioma and 16 with benign asbestos-related pleural disease were studied. Seven patients with malignant mesothelioma had no history of asbestos exposure, while the remaining 58 patients were exposed. Forty-three of the 49 patients (88%) with malignant mesothelioma had a positive 67gallium scan including 36 of the 42 (86%) patients with asbestos exposure and all 7 patients without a history of asbestos exposure. Three of 16 patients (19%) with benign asbestos-related pleural disease had a positive scan. 67Gallium radionuclide imaging is nonspecific but may be valuable in noninvasive monitoring of asbestos-exposed populations, which have a high risk for the late development of benign and/or malignant pleural disease.

  18. Process for producing gallium-containing solution from aluminum smelting dust

    SciTech Connect

    Ikeda, H.; Matsui, S.; Era, A.

    1988-02-16

    A process for producing a gallium-containing solution from aluminum smelting dust is described comprising mixing aluminum smelting dust with 5 to 50% by weight of an alkaline flux selected from the group consisting of sodium carbonate, sodium hydroxide, potassium carbonate, potassium hydroxide and mixtures thereof, heating the mixture to a temperature sufficient to roast the mixture without fusing the mixture, leaching the roasted mixture at a temperature of 80/sup 0/C. to 100/sup 0/C. with a mineral acid selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid and mixtures thereof to preferentially solubilize gallium from other material in the roasted mixture, and filtering the leached mixture to separate the solubilized gallium solution therefrom.

  19. Quantitative separation of gallium from other elements by cation-exchange chromatography

    SciTech Connect

    van der Walt, T.N.; Strelow, F.W.E.

    1983-02-01

    Trace amounts and up to 1.5 mg of gallium can be separated from up to gram amounts of Al, Cd, Cu, In, Mn, Ni, Pb, U(VI), and many other elements by eluting these elements with 8.0 M hydrochloric acid from a column containing 13.0 mL (3.0 g) of AG 50W-X4 cation-exchange resin of 100-200 mesh particle size in the H-form. Gallium can be separated from up to 2 g of iron(II) and up to 10 mg of scandium by eluting the iron with 8.0 M hydrochloric acid containing 0.30% titanium(III) chloride and eluting the scandium with 7.0 M hydrochloric acid. The retained gallium is effectively eluted with 2.5 M hydrochloric acid. Separations are sharp and quantitative. 5 figures, 3 tables.

  20. Piecewise simulaton proton test of gallium arsenide and thin silicon solar cells

    NASA Technical Reports Server (NTRS)

    Peterson, D. G.; Billets, S. A.

    1984-01-01

    Gallium Arsenide (GaAs) solar cells are viewed as a potential primary power source on certain future Earth orbiting satellites. However, the relative merits of gallium arsenide over silicon in a space radiation environment are largely unknown because a general degradation model for gallium arsenide does not exist. The results of a test simulating the proton radiation environment existing in a polar orbit and the concomitant effects on GaAs and thin silicon (Si) solar cells are presented. The objectives and methodology of the simulation test were discussed. The electrical characteristics of GaAs and Si solar cells are given in graph form. It was concluded that GaAs cells are viable for use on satellites in low Earth orbit.

  1. Gallium-assisted growth of silicon nanowires by electron cyclotron resonance plasmas

    NASA Astrophysics Data System (ADS)

    Hernández, M. J.; Cervera, M.; Ruiz, E.; Pau, J. L.; Piqueras, J.; Avella, M.; Jiménez, J.

    2010-11-01

    The use of gallium droplets for growing Si nanowires (SiNWs) by electron cyclotron resonance plasmas is investigated. First, the relationship between evaporation time and resultant size of the gallium droplets is studied. Through the use of spectroscopic ellipsometry, the dependence of the surface plasmon resonance (SPR) energy on the droplet size is determined. From these gallium droplets, SiNWs were grown at 300 and 550 °C in electron cyclotron resonance plasmas containing SiH4, Ar, and H2. Scanning electron microscopy results show that tapered NWs are obtained for a wide range of growth conditions. Besides, it is found that H2 plays an important role in the parasitic axial growth of the SiNWs. Namely, H2 inhibits the radial growth and contributes dramatically to increasing the SiNW defects.

  2. Interplay of disorder and geometrical frustration in doped gadolinium gallium garnet

    NASA Astrophysics Data System (ADS)

    Woo, N.; Silevitch, D. M.; Ferri, C.; Ghosh, S.; Rosenbaum, T. F.

    2015-07-01

    The geometrically frustrated triangular antiferromagnet Gadolinium Gallium Garnet (Gd3Ga5O12 or GGG) exhibits a rich mix of short-range order and isolated quantum states. We investigate the effects of up to 1% neodymium substitution for gallium on the ac magnetic response at temperatures below 1 K in both the linear and nonlinear regimes. Substitutional disorder actually drives the system toward a more perfectly frustrated state, apparently compensating for the effects of imperfect gadolinium/gallium stoichiometry, while at the same time more closely demarcating the boundaries of isolated, coherent clusters composed of hundreds of spins. Optical measurements of the local Nd environment substantiate the picture of an increased frustration index with doping.

  3. Crystal chemistry and self-lubricating properties of monochalcogenides gallium selenide and tin selenide

    SciTech Connect

    Erdemir, A.

    1993-02-01

    This paper describes the fundamentals of the crystal chemistry and self-lubricating mechanisms of two monochalcogenides; tin selenide and gallium selenide. Specifically, it enumerates their inter-atomic array and bond structure in crystalline states, and correlates this fundamental knowledge with their self-lubricating capacity. Friction tests assessing the self-lubricating performance of gallium and tin selenides were carried out on a pin-on-disk machine. Specifically, large crystalline pieces of gallium selenide and tin selenide were cut and cleaved into flat squares and subsequently rubbed against the sapphire balls. In another case, the fine powders (particle size {approx} 50--100 {mu}m) of gallium selenide and tin selenide were manually fed into the sliding interfaces of 440C pins and 440C disks. For the specific test conditions explored, it was found that the friction coefficients of the sapphire/gallium selenide and sapphire/tin selenide pairs were {approx} 0.23 and {approx} 0.35, respectively. The friction coefficients of 440C pin/440C disk test pairs with gallium selenide and tin selenide powders were on the orders of {approx} 0.22 and {approx} 0.38, respectively. For comparison, a number of parallel friction tests were performed with MoS{sub 2} powders and compacts and the results of these tests were also reported. The friction data together with the crystal-chemical knowledge and the electron microscopic evidence supported the conclusion that the lubricity and self-lubricating mechanisms of these solids are closely related to their crystal chemistry and the nature of interlayer bonding.

  4. Thermal Cycling and High Temperature Reverse Bias Testing of Control and Irradiated Gallium Nitride Power Transistors

    NASA Technical Reports Server (NTRS)

    Patterson, Richard L.; Boomer, Kristen T.; Scheick, Leif; Lauenstein, Jean-Marie; Casey, Megan; Hammoud, Ahmad

    2014-01-01

    The power systems for use in NASA space missions must work reliably under harsh conditions including radiation, thermal cycling, and exposure to extreme temperatures. Gallium nitride semiconductors show great promise, but information pertaining to their performance is scarce. Gallium nitride N-channel enhancement-mode field effect transistors made by EPC Corporation in a 2nd generation of manufacturing were exposed to radiation followed by long-term thermal cycling and testing under high temperature reverse bias conditions in order to address their reliability for use in space missions. Result of the experimental work are presented and discussed.

  5. Percolation of gallium dominates the electrical resistance of focused ion beam deposited metals

    SciTech Connect

    Faraby, H.; DiBattista, M.; Bandaru, P. R.

    2014-04-28

    Metal deposition through focused ion beam (FIB) based systems is thought to result in material composed of the primary metal from the metallo-organic precursor in addition to carbon, oxygen, and gallium. We determined, through electrical resistance and chemical composition measurements on a wide range of FIB deposited platinum and tungsten lines, that the gallium ion (Ga{sup +}) concentration in the metal lines plays the dominant role in controlling the electrical resistivity. Effective medium theory, based on McLachlan's formalisms, was used to describe the relationship between the Ga{sup +} concentration and the corresponding resistivity.

  6. Patterns of gallium-67 scintigraphy in patients with acquired immunodeficiency syndrome and the AIDS related complex

    SciTech Connect

    Bitran, J.; Bekerman, C.; Weinstein, R.; Bennett, C.; Ryo, U.; Pinsky, S.

    1987-07-01

    Thirty-two patients with AIDS related complex (ARC) or acquired immunodeficiency syndrome (AIDS) underwent /sup 67/Ga scans as part of their evaluation. Three patterns of /sup 67/Ga biodistribution were found: lymph node uptake alone; diffuse pulmonary uptake; normal scan. Gallium-67 scans were useful in identifying clinically occult Pneumocystis carinii pneumonia in seven of 15 patients with ARC who were asymptomatic and had normal chest radiographs. Gallium scans are a useful ancillary procedure in the evaluation of patients with ARC or AIDS.

  7. Results of the Gallium-Clad Phase 3 and Phase 4 tasks (canceled prior to completion)

    SciTech Connect

    Morris, R.N.

    1998-08-01

    This report summarizes the results of the Gallium-Clad interactions Phase 3 and 4 tasks. Both tasks were to involve examining the out-of-pile stability of residual gallium in short fuel rods with an imposed thermal gradient. The thermal environment was to be created by an electrical heater in the center of the fuel rod and coolant flow on the rod outer cladding. Both tasks were canceled due to difficulties with fuel pellet fabrication, delays in the preparation of the test apparatus, and changes in the Fissile Materials Disposition program budget.

  8. Gallium-SPECT in the detection of prosthetic valve endocarditis and aortic ring abscess

    SciTech Connect

    O'Brien, K.; Barnes, D.; Martin, R.H.; Rae, J.R. )

    1991-09-01

    A 52-yr-old man who had a bioprosthetic aortic valve developed Staphylococcus aureus bacteremia. Despite antibiotic therapy he had persistent pyrexia and developed new conduction system disturbances. Echocardiography did not demonstrate vegetations on the valve or an abscess, but gallium scintigraphy using SPECT clearly identified a focus of intense activity in the region of the aortic valve. The presence of valvular vegetations and a septal abscess was confirmed at autopsy. Gallium scintigraphy, using SPECT, provided a useful noninvasive method for the demonstration of endocarditis and the associated valve ring abscess.

  9. The clinical significance of radionuclide bone and gallium scanning in osteomyelitis of the head and neck

    SciTech Connect

    Noyek, A.M.; Kirsh, J.C.; Greyson, N.D.; Wortzman, G.; Jazrawy, H.; Freeman, J.L.; Blair, R.L.; Chapnik, J.S.

    1984-05-01

    Osteomyelitis of the head and neck remains a difficult clinical problem both in diagnosis and treatment evaluation. The purpose of this manuscript is to review our clinical experience with 25 cases of osteomyelitis distributed evenly among the temporal bone and skull base, the paranasal sinuses, and the mandible. Radionuclide bone and gallium scan images accurately depicted the biologic activity of the disease process and permitted accurate treatment evaluation and patient monitoring. This work demonstrates the potentials and limitations of radionuclide imaging with bone and gallium scan agents and attempts to define a role for their contemporary use in the management of osteomyelitis of the head and neck.

  10. Growth of epitaxial bismuth and gallium substituted lutetium iron garnet films by pulsed laser deposition

    SciTech Connect

    Leitenmeier, Stephan; Heinrich, Andreas; Lindner, Joerg K. N.; Stritzker, Bernd

    2006-04-15

    Epitaxial bismuth and gallium substituted lutetium iron garnet thin films have been grown on (100) oriented gadolinium gallium garnet Gd{sub 3}Ga{sub 5}O{sub 12} substrates by pulsed laser deposition. The films have been studied using x-ray diffraction, high resolution x-ray diffraction, Rutherford backscattering spectroscopy, transmission electron microscopy, and electron diffraction. We obtained smooth films with thicknesses between 0.3 and 1.0 {mu}m showing good crystalline quality and epitaxial growth.

  11. Phase Tuning of Nanostructured Gallium Oxide via Hybridization with Reduced Graphene Oxide for Superior Anode Performance in Li-Ion Battery: An Experimental and Theoretical Study.

    PubMed

    Patil, Sharad B; Kim, In Young; Gunjakar, Jayavant L; Oh, Seung Mi; Eom, Taedaehyeong; Kim, Hyungjun; Hwang, Seong-Ju

    2015-08-26

    The crystal phase of nanostructured metal oxide can be effectively controlled by the hybridization of gallium oxide with reduced graphene oxide (rGO) at variable concentrations. The change of the ratio of Ga2O3/rGO is quite effective in tailoring the crystal structure and morphology of nanostructured gallium oxide hybridized with rGO. This is the first example of the phase control of metal oxide through a change of the content of rGO hybridized. The calculations based on density functional theory (DFT) clearly demonstrate that the different surface formation energy and Ga local symmetry of Ga2O3 phases are responsible for the phase transition induced by the change of rGO content. The resulting Ga2O3-rGO nanocomposites show promising electrode performance for lithium ion batteries. The intermediate Li-Ga alloy phases formed during the electrochemical cycling are identified with the DFT calculations. Among the present Ga2O3-rGO nanocomposites, the material with mixed α-Ga2O3/β-Ga2O3/γ-Ga2O3 phase can deliver the largest discharge capacity with the best cyclability and rate characteristics, highlighting the importance of the control of Ga2O3/rGO ratio in optimizing the electrode activity of the composite materials. The present study underscores the usefulness of the phase-control of nanostructured metal oxides achieved by the change of rGO content in exploring novel functional nanocomposite materials. PMID:26258574

  12. Calculation of Gallium-metal-Arsenic phase diagrams

    NASA Technical Reports Server (NTRS)

    Scofield, J. D.; Davison, J. E.; Ray, A. E.; Smith, S. R.

    1991-01-01

    Electrical contacts and metallization to GaAs solar cells must survive at high temperatures for several minutes under specific mission scenarios. The determination of which metallizations or alloy systems that are able to withstand extreme thermal excursions with minimum degradation to solar cell performance can be predicted by properly calculated temperature constitution phase diagrams. A method for calculating a ternary diagram and its three constituent binary phase diagrams is briefly outlined and ternary phase diagrams for three Ga-As-X alloy systems are presented. Free energy functions of the liquid and solid phase are approximated by the regular solution theory. Phase diagrams calculated using this method are presented for the Ga-As-Ge and Ga-As-Ag systems.

  13. Rapid Thermal Processing of Zinc: Gallium-Arsenide

    NASA Astrophysics Data System (ADS)

    Dobkin, Daniel Mark

    The processing of semiconductor devices involves exposure of the semiconducting material to elevated temperatures for such purposes as removal of damage and emplacement of dopants. Gallium Arsenide (GaAs) is a semiconductor of interest for discrete devices and IC's owing to its high electron mobility and compatibility with optoelectronic devices; however, this material tends to undergo surface decomposition at high temperatures due to the release of the volatile component (As), unless special precautions are taken. We have studied Zn diffusion in, and surface modification of, GaAs using thermal cycle times of a few seconds (herein referred to as Rapid Thermal Processing, or RTP) and a simple proximity capping technique to prevent surface decomposition. A pre-treatment with aqueous Ru has enabled us to electroplate thin (100 (ANGSTROM))layers of Zn/ZnO directly on the GaAs surface. These layers can serve as a dopant source during RTP, allowing the formation of thin, heavily-doped p+ layers whose properties have been characterized as a function of RTP parameters. The layers also lead to modification of the GaAs surface properties under appropriate processing conditions, causing Al contacts deposited thereon to display Schottky barrier heights of 0.8 to 1.3 eV, compared to 0.7 to 0.8 eV for contacts fabricated by standard methods. Preliminary analyses of the properties of these contacts lead us to suggest that lateral inhomogeneity plays an important role in their electrical behavior. We have utilized the diffusion process to fabricate discrete junction field-effect transistors in GaAs, and employed surface modification to obtain Schottky-gate FET's (MESFET's) with increased barrier heights. In both cases devices with well-behaved DC characteristics were obtained, verifying the applicability of these techniques to semiconductor fabrication.

  14. Synthesis and characterisation of chromium lutetium gallium garnet solid solution

    SciTech Connect

    Galindo, R.; Badenes, J.A. . E-mail: jbadenes@qio.uji.es; Llusar, M.; Tena, M.A.; Monros, G.

    2007-03-22

    The chromium lutetium gallium garnet system has been studied. Samples with 2xCaOxCr{sub 2}O{sub 3}(3 - 2x)Lu{sub 2}O{sub 3}5Ga{sub 2}O{sub 3} (x = 0.025, 0.05, 0.075, 0.1, 0.2 and 0.3,) and xCr{sub 2}O{sub 3}(3 - x)Lu{sub 2}O{sub 3}5Ga{sub 2}O{sub 3} (x = 0, 0.05, 0.075 and 0.3) compositions have been prepared in Ca,Cr:LGG and Cr:LGG systems, respectively. Samples were prepared by ceramic method, fired at 1250 deg. C/6 h and characterised by XRD, lattice parameters, UV-vis-NIR spectroscopy, CIE L * a * b * measurements and SEM/EDX. Results indicate that Ca,Cr:LGG and Cr:LGG solid solutions are obtained. In Cr:LGG system only Cr(III) is stabilised in octahedral positions substituting for Lu(III) and Ga(III). Both Cr(III) and Cr(IV) are present in Ca,Cr:LGG. The calcium is a charge compensator to stabilise Cr(IV) and this is the predominant oxidation state up to x = 0.075 composition. From this composition, Cr(III) becomes more stabilised in garnet lattice. Cr(IV) occupies generally tetrahedral and dodecahedral sites substituting for Ga(III) and Lu(III), while Cr(III) is in octahedral site substituting for Ga(III)

  15. Indium Phosphide Window Layers for Indium Gallium Arsenide Solar Cells

    NASA Technical Reports Server (NTRS)

    Jain, Raj K.

    2005-01-01

    Window layers help in reducing the surface recombination at the emitter surface of the solar cells resulting in significant improvement in energy conversion efficiency. Indium gallium arsenide (In(x)Ga(1-x)As) and related materials based solar cells are quite promising for photovoltaic and thermophotovoltaic applications. The flexibility of the change in the bandgap energy and the growth of InGaAs on different substrates make this material very attractive for multi-bandgap energy, multi-junction solar cell approaches. The high efficiency and better radiation performance of the solar cell structures based on InGaAs make them suitable for space power applications. This work investigates the suitability of indium phosphide (InP) window layers for lattice-matched In(0.53)Ga(0.47)As (bandgap energy 0.74 eV) solar cells. We present the first data on the effects of the p-type InP window layer on p-on-n lattice-matched InGaAs solar cells. The modeled quantum efficiency results show a significant improvement in the blue region with the InP window. The bare InGaAs solar cell performance suffers due to high surface recombination velocity (10(exp 7) cm/s). The large band discontinuity at the InP/InGaAs heterojunction offers a great potential barrier to minority carriers. The calculated results demonstrate that the InP window layer effectively passivates the solar cell front surface, hence resulting in reduced surface recombination and therefore, significantly improving the performance of the InGaAs solar cell.

  16. Ultra-thin film nanostructured gallium arsenide solar cells

    NASA Astrophysics Data System (ADS)

    Kang, Yangsen; Chen, Yusi; Huo, Yijie; Zhao, Li; Jia, Jieyang; Deng, Huiyang; Harris, James S.

    2014-11-01

    State-of-the-art III-V cells have reached the highest energy conversion efficiency among all types of solar cells. However, these cells are not applicable to widespread terrestrial solar energy system yet due to the high cost of epitaxial growth. Ultra-thin film absorbers with advanced light management is one of the most promising solutions to drive down the cost. In this paper, we present an ultra-thin film nano-window gallium arsenide (GaAs) solar cell design. This ultrathin cell consists of a nano-structured Al0.8Ga0.2As window layer on the front side to reduce the reflection and to trap the light, and a metal reflector on the back side to further increase the light path. The 300 nm thick GaAs cell with Al0.8Ga0.2As nano-window shows a broad band absorption enhancement from visible to near infrared (NIR), achieving a spectrally averaged absorption of 94% under normal incidence. In addition, this cell shows excellent angular absorption properties, achieving over 85% spectral averaged absorption at up to 60 degree off normal incidence. Meanwhile, this structure with planar junction and nano-window has solved the issue of low fill factor and low open-circuit voltage in nano-structured GaAs solar cell. A nano-window cell with a 3 μm thick GaAs junction demonstrated an open circuit voltage of 0.9V.

  17. Immunosensing platform based on gallium nanoparticle arrays on silicon substrates.

    PubMed

    García Marín, Antonio; Hernández, María Jesús; Ruiz, Eduardo; Abad, Jose María; Lorenzo, Encarnación; Piqueras, Juan; Pau, Jose Luis

    2015-12-15

    Gallium nanoparticles (GaNPs) of different sizes are deposited on Si(100) substrates by thermal evaporation. Through ellipsometric analysis, it is possible to investigate the plasmonic effects in the GaNPs and exploit them to develop biosensors. The excitation of the resonant modes for certain incidence angles leads to negative values of the imaginary part of the pseudodielectric function (<εi>) obtained in ellipsometry. Furthermore, there is an abrupt sign change when the difference between the phase shifts of p- and s-polarization components reaches 180° at an energy of around 3.15 eV. At that energy, reversal of the polarization handedness (RPH) occurs for an elliptically-polarized input beam. The energy of the RPH condition reduces as the evaporation time increases. The slope of <εi> at the RPH condition is extremely sensitive to changes in the surrounding medium of the NP surface and prompts the use of the GaNP/Si system as sensor platform. Fourier transformed infrared spectroscopy (FTIR) is used before and after functionalization with 3,3'-dithiodipropionic acid di(N-succinimidyl ester) and a glutathione-specific antibody to confirm the chemical modification of the sample surface. The developed immunosensor is exposed to different concentrations of glutathione (GSH) showing a linear relationship between the slope of the pseudodielectric function at the RPH condition and the GSH concentration. The immunosensor shows a limit of detection of 10nM enabling its use for the detection of low GSH levels in different medical conditions. PMID:26276543

  18. Role of Oxidative Stress in the Induction of Metallothionein-2A and Heme Oxygenase-1 Gene Expression by the Antineoplastic Agent Gallium Nitrate in Human Lymphoma Cells

    PubMed Central

    Yang, Meiying; Chitambar, Christopher R.

    2008-01-01

    The mechanisms of action of gallium nitrate, an antineoplastic drug, are only partly understood. Using a DNA microarray to examine genes induced by gallium nitrate in CCRF-CEM cells, we found that gallium increased metallothionein-2A (MT2A) and heme oxygenase-1 (HO-1) gene expression and altered the levels of other stress-related genes. MT2A and HO-1 were increased after 6 and 16 h of incubation with gallium nitrate. An increase in oxidative stress, evidenced by a decrease in cellular GSH and GSH/GSSG ratio, and an increase in dichlorodihydrofluoroscein (DCF) fluorescence, was seen after 1 – 4 h incubation of cells with gallium nitrate. DCF fluorescence was blocked by the mitochondria-targeted antioxidant mitoquinone. N-acetyl-L-cysteine blocked gallium-induced MT2A and HO-1 expression and increased gallium’s cytotoxicity. Studies with a zinc-specific fluoroprobe suggested that gallium produced an expansion of an intracellular labile zinc pool, suggesting an action of gallium on zinc homeostasis. Gallium nitrate increased the phosphorylation of p38 mitogen-activated protein kinase and activated Nrf-2, a regulator of HO-1 gene transcription. Gallium-induced Nrf-2 activation and HO-1 expression were diminished by a p38 MAP kinase inhibitor. We conclude that gallium nitrate induces cellular oxidative stress as an early event which then triggers the expression of HO-1 and MT2A through different pathways. PMID:18586083

  19. Ductile alloy and process for preparing composite superconducting wire

    DOEpatents

    Verhoeven, John D.; Finnemore, Douglas K.; Gibson, Edwin D.; Ostenson, Jerome E.

    1983-03-29

    An alloy for the commercial production of ductile superconducting wire is prepared by melting together copper and at least 15 weight percent niobium under non-oxygen-contaminating conditions, and rapidly cooling the melt to form a ductile composite consisting of discrete, randomly distributed and orientated dendritic-shaped particles of niobium in a copper matrix. As the wire is worked, the dendritric particles are realigned parallel to the longitudinal axis and when drawn form a plurality of very fine ductile superconductors in a ductile copper matrix. The drawn wire may be tin coated and wound into magnets or the like before diffusing the tin into the wire to react with the niobium. Impurities such as aluminum or gallium may be added to improve upper critical field characteristics.

  20. Ductile alloy and process for preparing composite superconducting wire

    DOEpatents

    Verhoeven, J.D.; Finnemore, D.K.; Gibson, E.D.; Ostenson, J.E.

    An alloy for the commercial production of ductile superconducting wire is prepared by melting together copper and at least 15 weight percent niobium under non-oxygen-contaminating conditions, and rapidly cooling the melt to form a ductile composite consisting of discrete, randomly distributed and oriented dendritic-shaped particles of niobium in a copper matrix. As the wire is worked, the dendritic particles are realigned parallel to the longitudinal axis and when drawn form a plurality of very fine ductile superconductors in a ductile copper matrix. The drawn wire may be tin coated and wound into magnets or the like before diffusing the tin into the wire to react with the niobium. Impurities such as aluminum or gallium may be added to improve upper critical field characteristics.

  1. Gallium-cladding compatibility testing plan: Phase 3 -- Test plan for centrally heated surrogate rodlet test. Revision 2

    SciTech Connect

    Morris, R.N.; Baldwin, C.A.; Wilson, D.F.

    1998-07-01

    The Fissile Materials Disposition Program (FMDP) is investigating the use of weapons grade plutonium in mixed oxide (MOX) fuel for light-water reactors (LWR). Commercial MOX fuel has been successfully used in overseas reactors for many years; however, weapons derived fuel may differ from the previous commercial fuels because of small amounts of gallium impurities. A concern presently exists that the gallium may migrate out of the fuel, react with and weaken the clad, and thereby promote loss of fuel pin integrity. Phases 1 and 2 of the gallium task are presently underway to investigate the types of reactions that occur between gallium and clad materials. This is a Level-2 document as defined in the Fissile Materials Disposition Program Light-Water Reactor Mixed-Oxide Fuel Irradiation Test Project Plan. This Plan summarizes the projected Phase 3 Gallium-Cladding compatibility heating test and the follow-on post test examination (PTE). This work will be performed using centrally-heated surrogate pellets, to avoid unnecessary complexities and costs associated with working with plutonium and an irradiation environment. Two sets of rodlets containing pellets prepared by two different methods will be heated. Both sets will have an initial bulk gallium content of approximately 10 ppm. The major emphasis of the PTE task will be to examine the material interactions, particularly indications of gallium transport from the pellets to the clad.

  2. Irradiation effects of graphene-enhanced gallium nitride (GaN) metal-semiconductor-metal (MSM) ultraviolet photodetectors

    NASA Astrophysics Data System (ADS)

    Chiamori, Heather C.; Miller, Ruth; Suria, Ateeq; Broad, Nicholas; Senesky, Debbie G.

    2015-05-01

    Ultraviolet (UV) photodetectors are used for applications such as flame detection, space navigation, biomedical and environmental monitoring. Robust operation within large ranges of temperatures, radiation, salinity and/or corrosive chemicals require sensor materials with the ability to withstand and function reliably within these extreme harsh environments. For example, spacecraft can utilize a sun sensor (light-based sensor) to assist with determination of orientation and may be exposed to both ionizing radiation and extreme temperature swings during operation. Gallium nitride (GaN), a wide bandgap semiconductor material, has material properties enabling visible-blindness, tunable cutoff wavelength selection based on ternary alloy mole fraction, high current density, thermal/chemical stability and high radiation tolerance due to the strength of the chemical bond. Graphene, with outstanding electrical, optical and mechanical properties and a flat absorption spectrum from 300 to 2,500 nm, has potential use as a transparent conductor for GaN-based metal-semiconductor-metal (MSM) photodetectors. Here, graphene-enhanced MSM UV photodetectors are fabricated with transparent and conductive graphene interdigitated electrodes on thin film GaN-on-sapphire substrates serving as back-to-back Schottky contacts. We report on the irradiation response of graphene/GaN-based MSM UV photodetectors up to 750 krad total ionizing dose (TID) then tested under dark and UV light (365 nm) conditions. In addition, based on current-voltage measurements from 75 krad to 750 krad TID, calculated photodetector responsivity values change slightly by 25% and 11% at -5 V and -2 V, respectively. These initial findings suggest that graphene/GaN MSM UV photodetectors could potentially be engineered to reliably operate within radiation environments.

  3. Combined effect of gallium and carbon on the structure and magnetic properties of nanocrystalline SmFe9

    NASA Astrophysics Data System (ADS)

    Bessais, L.; Dorolti, E.; Djéga-Mariadassou, C.

    2006-04-01

    SmFe9-yGaxC carbides (0<=x<=1) were prepared by a two-step method of powder high-energy milling with annealing between 873 and 1200 K and a subsequent carbonation with heavy hydrocarbon at 693 K. The x-ray diffraction analysis with the Rietveld technique indicates an anisotropic volume expansion under carbonation slackened by the gallium substitution. The average saturation magnetic moment per Fe atom, measured with an applied field up to 200 kOe, increases slightly to 2.00 µB with Ga content. The Curie temperature, always 15 K above that of the homologous 2/17 carbides, is reduced by a dilution effect with Ga substitution and a concomitant increase of the negative Fe-Fe interactions. The Mössbauer spectra have been analysed on the basis of the binomial law related to the different Fe environments. The hyperfine parameter assignment to each individual crystallographic site was performed according to the correlation between isomer shift and Wigner-Seitz cell volumes calculated with a specific code in the P 1 space group allowing the splitting of the partially occupied atomic positions. The role of the C insertion is shown, on the one hand, by the increase of isomer shift due to the volume expansion with an enhancement of the charge transfer from the rare-earth atoms and, on the other hand, by the hyperfine field increase, pointing out the predominance of the negative core electron polarization term. The coercive field of 27 kOe, combined with a Curie temperature of 680 K, makes the alloy SmFe8.75Ga0.25C promising for further applications in the field of high-performance permanent magnets.

  4. Role of iron-binding proteins and enhanced capillary permeability on the accumulation of gallium-67

    SciTech Connect

    Tzen, K.Y.; Oster, Z.H.; Wagner, H.N. Jr.; Tsan, M.F.

    1980-01-01

    We studied the role of the iron-binding proteins transferrin and lactoferrin and of increased capillary permeability on the accumulation of gallium-67 in rabbits. Intramuscular injection of histamine caused accumulation of gallium-67 (injected iv as citrate), and of Tc-99m DTPA, at the im injection site. Normal saline and albumin did not. Intramuscular injection of transferrin or lactoferrin similarly caused Ga-67 uptake. No accumulation of Tc-99m DTPA was observed at the site of transferrin injection but there was a slight accumulation at the site of lactoferrin injection. Prior saturation of transferrin or lactoferrin with ferric ion abolished their effect on Ga-67 accmulation. Gallium-67, pre-bound to transferrin in vitro, did not accumulate at the site of histamine or transferrin injection, but there was a slight accumulation at the lactoferrin site. Our results suggest that either increased capillary permeability of iron-binding proteins can cause local uptake of Ga-67. Since these factors are present at sites of inflammation, they may contribute to the accumulation of gallium in inflammatory lesions.

  5. Influence of various factors on the accuracy of gallium-67 imaging for occult infection

    SciTech Connect

    Maderazo, E.G.; Hickingbotham, N.B.; Woronick, C.L.; Sziklas, J.J.

    1988-05-01

    To examine whether the results and interpretation of gallium-67 citrate imaging may be adversely influenced by factors present in compromised patients, we reviewed our 1-year experience in 69 patients in intensive care units, renal transplants, and those on hemodialysis. Our results indicate that it is an inappropriate diagnostic procedure for acute pancreatitis since seven of nine had false-negative results. Using loglinear modeling and chi-square analysis we found that treatment with antiinflammatory steroids, severe liver disease, end-stage renal disease, and renal transplantation with immunosuppressive therapy did not interfere with gallium-67 uptake. Increased rate of true-negative results in patients with end-stage renal disease was due to a greater and earlier use of the test in the febrile transplant patient and in hemodialysis patients with infections not amenable to diagnosis with gallium-67 scan (transient bacteremia and bacteriuria). We conclude that gallium-67 imaging is a useful diagnostic tool that, with the exception of acute pancreatitis, has very few false-negative results.

  6. Gallium arsenide integrated optical devices for high-speed diagnostic systems

    SciTech Connect

    McWright, G.; Lowry, M.; Takeuchi, E.; Murphy, G.; Tindall, W.; Koo, J.; Roeske, F.

    1987-01-01

    The design, fabrication, and evaluation of waveguide electro-optic modulators in gallium arsenide for application to high-speed diagnostic systems are discussed specifically. This paper is focused on high bandwidth, single event analog modulation, and radiation susceptibility of these devices.

  7. Infected cyst localization with gallium SPECT imaging in polycystic kidney disease

    SciTech Connect

    Amesur, P.; Castronuovo, J.J.; Chandramouly, B.

    1988-01-01

    This case report describes a 43-year-old woman with polycystic renal disease and cyst infection. Infected cysts of the left kidney were successfully localized with Ga-67 citrate SPECT imaging and CT. Other imaging, including planar gallium imaging, was helpful diagnostically, but could not determine the exact location of infection within the kidney.

  8. Case report: gallium study showing a rare form of multiple myeloma

    SciTech Connect

    Meyers, E.; Kasner, J.R.

    1981-12-01

    A case study is presented in which a rare form of multiple myeloma with soft tissue involvememt was diagnosed by a gallium scan using 3 mCi of Ga-67 citrate. Subsequent resting cardiac blood pool images suggested pericardial rather than myocardial involvement. (JMT)

  9. Radiographic and radionuclide imaging in multiple myeloma: the role of gallium scintigraphy: concise communication

    SciTech Connect

    Waxman, A.D.; Siemsen, J.K.; Levine, A.M.; Holdorf, D.; Suzuki, R.; Singer, F.R.; Bateman, J.

    1981-03-01

    Eighteen patients with multiple myeloma were studied using radiographs of the skeletal system, technetium phosphate bone scans, and gallium-67 scintigraphy. A total of 94 sites were used as the basis for comparison in these 18 patients. Radiographic sensitivity on a patient basis was 94%, and was 82% on a site basis. Bone scans were positive in 78% of patients and in 46% of sites. Gallium scans were positive in 56% of patients and in 40% of sites. In five of the 18 patients, gallium scans showed activity in abnormal sites wth a greater lesion-to-nonlesion ratio than did the bone scan. In this subgroup of patients, the disease was fulminant, and all died within 3 mo of their study. The finding of high gallium uptake in osseous sites that are normal or only slightly abnormal on bone scan has served to identify a subgroup of patients with rapidly progressive disease who may benefit from alternative treatment modalities such as radiation therapy.

  10. Skylab experiment performance evaluation manual. Appendix J: Experiment M555 gallium arsenide single crystal growth (MSFC)

    NASA Technical Reports Server (NTRS)

    Byers, M. S.

    1973-01-01

    Analyses for Experiment M555, Gallium Arsenide Single Crystal Growth (MSFC), to be used for evaluating the performance of the Skylab corollary experiments under preflight, inflight, and post-flight conditions are presented. Experiment contingency plan workaround procedure and malfunction analyses are presented in order to assist in making the experiment operationally successful.

  11. Uncooled pulsed cadmium sulfide and gallium arsenide lasers pumped longitudinally by an electron beam

    SciTech Connect

    Bogdankevich, O.V.; Zverev, M.M.; Kostin, N.N.; Kopyt, S.P.; Krasavina, E.M.; Kryukova, I.V.; Matveenko, E.V.; Pevtsov, V.F.; Ushakhin, V.A.; Yakushin, V.K.

    1985-07-01

    A report is given of the fabrication of multielement uncooled lasers with an output power of 17 MW per pulse in the case of cadmium sulfide and 4.5 MW in the case of gallium arsenide pumped longitudinally by an electron beam. Ways of improving the characteristics of these lasers are considered.

  12. Discordant gallium-67 and indium-111 leukocyte images in a suspected pelvic abscess

    SciTech Connect

    Intenzo, C.; Thakur, M.L.; Park, C.

    1984-11-01

    An Indium-111 labeled white blood cell scan suggested the presence of a pelvic abscess in a woman at four weeks postpartum. This was not identified on a subsequent gallium scan. This discrepancy can be attributed to the normal accumulation of white blood cells within the uterus at one month postpartum.

  13. Structure and optical properties of cubic gallium oxynitride synthesized by solvothermal route

    SciTech Connect

    Oberländer, Andreas; Kinski, Isabel; Zhu, Wenliang; Pezzotti, Giuseppe; Michaelis, Alexander

    2013-04-15

    Cubic gallium oxynitride was synthesized using a solvothermal processing route. Crystal structure, chemical composition, optical properties and the influence of heat treatment in either reactive or inert atmospheres have been investigated. Despite a strongly distorted lattice revealed using X-ray diffraction, the Raman active modes of a cubic gallium oxynitride structure could be observed. With diffusive reflectance UV–Vis spectroscopy a band gap at around 4.8 eV has been observed. Additionally, cathodoluminescence spectroscopy exhibited observable luminescence caused by defect-related transitions within the optical gap. Cathodoluminescence and photoluminescence spectra collected after heat treatments showed significant changes in the defect structure. In particular, for annealing in ammonia the main spectral modifications were related to the substitution of oxygen by nitrogen on anion sites. - Graphical abstract: CL spectra of gallium oxynitride: As-prepared and heat-treated at temperatures of 500 °C in different atmospheres. Highlights: ► Raman spectrum of cubic gallium oxynitride. ► Experimental determination of optical band gap. ► Shift of band gap energy due to heat treatment. ► Nitrogen incorporation leads to deep level acceptor states. ► Red shifted luminescence spectrum.

  14. Bilateral Comparison of Mercury and Gallium Fixed-Point Cells Using Standard Platinum Resistance Thermometer

    NASA Astrophysics Data System (ADS)

    Bojkovski, J.; Veliki, T.; Zvizdić, D.; Drnovšek, J.

    2011-08-01

    The objective of project EURAMET 1127 (Bilateral comparison of triple point of mercury and melting point of gallium) in the field of thermometry is to compare realization of a triple point of mercury (-38.8344 °C) and melting point of gallium (29.7646 °C) between the Slovenian national laboratory MIRS/UL-FE/LMK and the Croatian national laboratory HMI/FSB-LPM using a long-stem 25 Ω standard platinum resistance thermometer (SPRT). MIRS/UL/FE-LMK participated in a number of intercomparisons on the level of EURAMET. On the other hand, the HMI/LPM-FSB laboratory recently acquired new fixed-point cells which had to be evaluated in the process of intercomparisons. A quartz-sheathed SPRT has been selected and calibrated at HMI/LPM-FSB at the triple point of mercury, the melting point of gallium, and the water triple point. A second set of measurements was made at MIRS/UL/FE-LMK. After its return, the SPRT was again recalibrated at HMI/LPM-FSB. In the comparison, the W value of the SPRT has been used. Results of the bilateral intercomparison confirmed that the new gallium cell of the HMI/LPM-FSB has a value that is within uncertainty limits of both laboratories that participated in the exercise, while the mercury cell experienced problems. After further research, a small leakage in the mercury fixed-point cell has been found.

  15. Gallium-67 breast uptake in a patient with hypothalamic granuloma (sarcoid)

    SciTech Connect

    Vazquez, R.; Oates, E.; Sarno, R.C.; Fay, J.; Gale, D.R.

    1988-01-01

    An unusual case is presented of bilateral breast uptake of (/sup 67/Ga)citrate in a patient with a hypothalamic granuloma in the absence of galactorrhea is presented. A possible mechanism for this incidental finding is elevated prolactin levels, as other causes of gallium breast uptake such as drug therapy, and intrinsic breast disease, were not present.

  16. Preliminary results of bench implementation for the study of terahertz amplification in gallium nitride quantum wells

    NASA Astrophysics Data System (ADS)

    Laurent, T.; Nouvel, P.; Torres, J.; Chusseau, L.; Palermo, C.; Varani, L.; Cordier, Y.; Faurie, J.-P.; Beaumont, B.; Starikov, E.; Shiktorov, P.; Gruinskis, V.

    2009-11-01

    We present continuous-wave terahertz spectroscopic results obtained with a photomixing emitter and a bolometric detection. The tested elements are candidates for a further cryogenic THz experiment which will consist to demonstrate the effective amplification by optical phonon transit time resonance in gallium nitride quantum wells.

  17. Electro-optic modulator for infrared laser using gallium arsenide crystal

    NASA Technical Reports Server (NTRS)

    Walsh, T. E.

    1968-01-01

    Gallium arsenide electro-optic modulator used for infrared lasers has a mica quarter-wave plate and two calcite polarizers to amplitude or phase modulate an infrared laser light source in the wavelength range from 1 to 3 microns. The large single crystal has uniformly high resistivities, is strain free, and comparable in quality to good optical glass.

  18. Turbine Blade Alloy

    NASA Technical Reports Server (NTRS)

    MacKay, Rebecca

    2001-01-01

    The High Speed Research Airfoil Alloy Program developed a fourth-generation alloy with up to an +85 F increase in creep rupture capability over current production airfoil alloys. Since improved strength is typically obtained when the limits of microstructural stability are exceeded slightly, it is not surprising that this alloy has a tendency to exhibit microstructural instabilities after high temperature exposures. This presentation will discuss recent results obtained on coated fourth-generation alloys for subsonic turbine blade applications under the NASA Ultra-Efficient Engine Technology (UEET) Program. Progress made in reducing microstructural instabilities in these alloys will be presented. In addition, plans will be presented for advanced alloy development and for computational modeling, which will aid future alloy development efforts.

  19. Cobalt-base alloy

    NASA Technical Reports Server (NTRS)

    Dreshfield, R. L.; Sandrock, G. D.; Freche, J. C. (Inventor)

    1973-01-01

    A microstructurally stable, high strength cobalt based alloy for use at elevated temperatures to 2125 F was developed. The alloys are particularly directed for use in stators and other low stress components in advanced gas turbines.

  20. Functionalization of nitrogen-doped carbon nanotubes with gallium to form Ga-CNx-multi-wall carbon nanotube hybrid materials

    NASA Astrophysics Data System (ADS)

    Simmons, Trevor J.; Hashim, Daniel P.; Zhan, Xiaobo; Bravo-Sanchez, Mariela; Hahm, Myung Gwan; López-Luna, Edgar; Linhardt, Robert J.; Ajayan, Pulickel M.; Navarro-Contreras, Hugo; Vidal, Miguel A.

    2012-08-01

    In an effort to combine group III-V semiconductors with carbon nanotubes, a simple solution-based technique for gallium functionalization of nitrogen-doped multi-wall carbon nanotubes has been developed. With an aqueous solution of a gallium salt (GaI3), it was possible to form covalent bonds between the Ga3+ ion and the nitrogen atoms of the doped carbon nanotubes to form a gallium nitride-carbon nanotube hybrid at room temperature. This functionalization was evaluated by x-ray photoelectron spectroscopy, energy dispersive x-ray spectroscopy, Raman spectroscopy, scanning electron microscopy and transmission electron microscopy

  1. [Spectrophotometric determination of scandium,gallium and vanadium in white cabbage leaves].

    PubMed

    Buhl, F; Połedniok, J

    1997-01-01

    Scandium, gallium and vanadium contents in plants is on the ppm level, although plants from industrial areas can show higher concentrations of these elements. In Department of Analytical Chemistry of Silesian University there have been elaborated new, sensitive, spectrophotometric methods of determination of scandium, gallium and vanadium using Chrome Azurol S (CAS) and Sterinol (ST). The aim of this study was the application of these methods in analysis of cultivated plants from polluted regions. White cabbage from Upper Silesia was chosen. Because the spectrophotometric methods are not selective, scandium, gallium and vanadium should be preliminary separated from interfering elements. The solvent reaction was applied for the isolation from main and trace components of investigated material. Tienoiltrifluoracetone solution in xylene was used for the extraction of scandium, mesithyloxide for vanadium and n-butyl acetate--for gallium. Interfering and not separated Fe(III) was isolated using the extraction with acetylacetone solution in CHCl3 in the case of scandium and the reduction to Fe(II) by ascorbic acid in the case of gallium and vanadium. Due to influence of Fe(II) on the vanadium determination, KCN was used as a masking agent directly after the reduction. Scandium, gallium and vanadium were determined in 6 independent samples of white cabbage after dry or wet mineralization and contents of these leemnets were found from calibration graphs. Obtain results were checked by the internal standard addition method and Atomic Emission Spectrometry Method (ICP AES). The amounts of gallium and vanadium in white cabbage from Upper Silesia District determined by elaborated methods are in good correlation with a literature data, although the contents of vanadium are on the toxic level. The scandium concentration is higher than in plants from not industrial areas. The standard recovery is satisfactory. The Atomic Emission Spectrometry Method gave comparable results. The proposed the spectrophotometric methods are sensitive, precise and economical too, because they require only small amounts of reagents and simple not expensive apparatus. The methods can be recommended for many laboratories to the analytical control of white cabbage and after adaptation to the other plant material analysis. PMID:9562804

  2. Growth and characterization of thin and thick gallium nitride

    NASA Astrophysics Data System (ADS)

    Mastro, Michael Anthony

    2001-07-01

    The III-nitrides have received considerable attention in recent years for applications that require a wide band gap semiconductor. Specifically, short wavelength light emitters are required for full color displays, laser printers, high-density information storage, and underwater communication. High-temperature and high-power devices are needed for a number of applications including avionics, automobile engines and future advanced power distribution systems. Unfortunately, III-nitride substrates are not available. This dissertation explores three alternative substrates (LiGaO2, LiAlO2, and Si) for the growth of thick and potentially freestanding GaN substrates. The requirement to grow a protective layer of GAN by metal organic chemical vapor deposition (MOCVD) and the need for high rate deposition by hydride vapor phase epitaxy (HVPE) motivated the development of a single deposition system capable of growing in both modes. The successful growth of high quality GaN on LiGaO2 by MOCVD was first demonstrated. Nitridation of the LiGaO2 substrate using NH3 prior to growth leads to the reconstruction of the substrate surface and to the formation of a thin layer of nitrided material having the same orientation as the substrate. It was found that the thick GaN layer grown by HVPE spontaneously separated from the underlying LiGaO2 substrate upon cooling if proper nitridation was performed. This then eliminates the need for substrate removal by HCl etching and gives a reusable template substrate. The related substrate LiAlO2 is also closely lattice matched to GaN. LiAlO2, however, is more stable, particularly in an HCl ambient making it suitable for thick HVPE growth of GaN. Finally, it was shown that epitaxial GaN could be fabricated by a low-temperature deposition sequence on silicon substrates. Measurements revealed that a thin compliant SiOx layer was an effective intermediate layer for the GaN film grown epitaxially on Si. The deposition temperature of 560°C is one of the lowest deposition temperatures reported for single crystal GaN by vapor phase epitaxy. A study of GaN annealed in HCl, H2, NH3 and N 2 ambients was performed. It was found that films grown by MOCVD followed a dissociative sublimation mechanism, while HVPE films decomposed to yield liquid gallium.

  3. Spin-phonon coupling and ferroelectricity in magnetoelectric gallium ferrite

    NASA Astrophysics Data System (ADS)

    Mukherjee, Somdutta

    2014-03-01

    Gallium ferrite (GaFeO3 or GFO) is a low temperature ferrimagnet and room temperature piezoelectric wherein the magnetic transition temperature (TC) could be tailored to room temperature and above by tuning the stoichiometry and processing conditions. Such tunability of the magnetic transition temperature renders GFO a unique perspective in the research of multiferroics to potentially demonstrate room temperature magnetoelectric effect attractive for futuristic digital memory applications. Recent studies in several transition metal oxides highlight the importance of spin-phonon coupling in designing novel multiferroics by means of strain induced phase transition. In the present work, we have systematically studied the evolution of phonons in good quality samples of GFO across the TC using Raman spectroscopy. Using the phonon softening behavior and nearest neighbor spin-spin correlation function below TC we estimated spin-phonon coupling strength in the magnetically ordered state. In the process, we also show, for the first time, the presence of a spin glass phase in GFO where the spin-glass transition has a signature of abrupt change in spin-phonon coupling strength. Though GFO is piezoelectric and crystallizes in polar Pc21n symmetry, its ferroelectric nature remained controversial probably due to the large leakage current in the bulk material. To address this issue, we deposited epitaxial thin film on single crystalline yttria stabilized zirconia (YSZ) substrate using indium tin oxide (ITO) as a bottom conducting layer. We demonstrate clear evidence of room temperature ferroelectricity in the thin films from the 180o phase shift of the piezoresponse upon switching the electric field. Further, suppression of dielectric anomaly in presence of an external magnetic field clearly reveals a pronounced magneto-dielectric coupling across the magnetic transition temperature. In addition, using first principles calculations we elucidate that Fe ions are not only responsible for ferrimagnetism as observed earlier, but give rise to the observed ferroelectricity also, making GFO an unique single phase multiferroic. I thank to my collaborators (Somdutta Mukherjee, Amritendu Roy, Sushil Auluck, Rajendra Prasad, Rajeev Gupta,and Ashish Garg) for their contributions in the present work. This work was partially funded by DST, India.

  4. Development of micro-electromechanical systems in gallium nitride

    NASA Astrophysics Data System (ADS)

    Strittmatter, Robert P.

    This thesis is focused on the development of micro-electromechanical systems (MEMS) in III-V nitride semiconductors, with a primary emphasis on gallium-nitride (GaN). Though GaN exhibits unique properties that make it an effective platform for MEMS devices, to date, this field of study has received almost no attention in the nitride community. As a result, the research outlined in this thesis represents the very first steps in the development of GaN for this application. A critical issue for the advancement of GaN MEMS is the development of transducers to actuate and sense motion in deformable microstructures. In the second chapter of this text, we present two classes (and four instances) of strain transducers, native to GaN, which take advantage of its large piezoelectric constants. Unlike in conventional insulating crystals, the presence of free charge carriers in the semiconductor has a strong bearing on its response to strain. The action of piezoelectricity within a semiconductor allows for a family of versatile and sensitive transducers in GaN. Another basic issue facing this new field is the establishment of a fabrication technology to create suspended structures on the micron and nanometer scale. In Chapter 3, we describe two processes that were developed to fashion a wide range of MEMS devices in both p-type and n-type GaN. Each process exploits a distinct electrochemical etch which is dopant selective, the two etches being complementary. In one process, a photo-electrochemical method was adapted to undercut p-GaN epilayers that were grown on top of n-type sacrificial layers. For the other, a novel anodic etch was developed to undercut n-GaN layers. Both methods feature high dopant selectivity, rapid undercutting rates, and lateral etch control. The final chapter brings together both major research thrusts in the study of resonant cantilevers with integrated piezoelectric transducers. These devices are evaluated in terms of two important benchmarks: (i) the sensitivity to detect endpoint displacement, and (ii) the quality factor of the resonance. In the former case, the devices met up with our theoretical expectations; in the latter, no fundamental material limitation was found.

  5. An investigation into the thermally grown oxide on gallium nitride

    NASA Astrophysics Data System (ADS)

    Wolter, Scott David

    The thermally grown oxide on GaN has been studied to provide information concerning the stability of GaN in oxidizing environments and the potential of the native oxide for use in device applications. Thick GaN epilayers and GaN powders were exposed to dry air at 450°C to 1000°C for periods of 1 to 25h. Following oxidation, the epilayers were analyzed by x-ray photoelectron spectroscopy and glancing incidence x-ray diffraction, and the powders were analyzed by x-ray diffraction in the Bragg-Brentano geometry. For both the GaN films and powders, significant oxidation was observed at 900°C, and the oxide was identified as monoclinic beta-Ga2O3. Oxidation in dry air resulted in roughening of the oxide/GaN interface and oxide surface. In the temperature range 900°C to 1000°C, linear kinetics were observed for times up to 10 h indicating an interfacial reaction mechanism as the rate limiting step for oxidation. An apparent activation energy of ˜3 x 105 J/mole was determined for this process. The early stages of thermal oxide growth on GaN epilayers oxidized in dry O2 were also studied using x-ray photoelectron spectroscopy and high resolution transmission electron microscopy. The formation of a thin, uniform dielectric layer (1.5nm--3.0nm thick) was uncovered. This layer grew epitaxially on the (0001) GaN and is believed to be a gallium oxynitride (Ga(x+2)N3xO(3--3x)). Atomic force microscopy revealed the formation of discrete oxide crystallites on top of this layer that become more numerous and grow with continued oxidation. The influence of the thin, uniform dielectric on the electrical properties and thermal stability of Pt contacts to n-GaN was subsequently evaluated. An increase in the effective barrier height, improved ideality factors, and reduced reverse bias leakage currents were observed for the Pt/thin insulator/n-GaN structures compared to those of the conventional Pt/n-GaN. Furthermore, the thin insulator was more effective in limiting the interdiffusion between the Pt and GaN when subjected to high temperatures, by theta-2theta x-ray diffraction and Auger electron spectroscopy depth profiles. The effectiveness of the Pt/thin insulator/n-GaN structures as a Schottky diode-like gas sensor was also investigated, and the structure was found to exhibit sensitivity to hydrogen at room temperature to 200°C.

  6. DELTA PHASE PLUTONIUM ALLOYS

    DOEpatents

    Cramer, E.M.; Ellinger, F.H.; Land. C.C.

    1960-03-22

    Delta-phase plutonium alloys were developed suitable for use as reactor fuels. The alloys consist of from 1 to 4 at.% zinc and the balance plutonium. The alloys have good neutronic, corrosion, and fabrication characteristics snd possess good dimensional characteristics throughout an operating temperature range from 300 to 490 deg C.

  7. PLUTONIUM-THORIUM ALLOYS

    DOEpatents

    Schonfeld, F.W.

    1959-09-15

    New plutonium-base binary alloys useful as liquid reactor fuel are described. The alloys consist of 50 to 98 at.% thorium with the remainder plutonium. The stated advantages of these alloys over unalloyed plutonium for reactor fuel use are easy fabrication, phase stability, and the accompanying advantuge of providing a means for converting Th/sup 232/ into U/sup 233/.

  8. SUPERCONDUCTING VANADIUM BASE ALLOY

    DOEpatents

    Cleary, H.J.

    1958-10-21

    A new vanadium-base alloy which possesses remarkable superconducting properties is presented. The alloy consists of approximately one atomic percent of palladium, the balance being vanadium. The alloy is stated to be useful in a cryotron in digital computer circuits.

  9. High strength alloys

    DOEpatents

    Maziasz, Phillip James; Shingledecker, John Paul; Santella, Michael Leonard; Schneibel, Joachim Hugo; Sikka, Vinod Kumar; Vinegar, Harold J.; John, Randy Carl; Kim, Dong Sub

    2012-06-05

    High strength metal alloys are described herein. At least one composition of a metal alloy includes chromium, nickel, copper, manganese, silicon, niobium, tungsten and iron. System, methods, and heaters that include the high strength metal alloys are described herein. At least one heater system may include a canister at least partially made from material containing at least one of the metal alloys. At least one system for heating a subterranean formation may include a tublar that is at least partially made from a material containing at least one of the metal alloys.

  10. High strength alloys

    DOEpatents

    Maziasz, Phillip James [Oak Ridge, TN; Shingledecker, John Paul [Knoxville, TN; Santella, Michael Leonard [Knoxville, TN; Schneibel, Joachim Hugo [Knoxville, TN; Sikka, Vinod Kumar [Oak Ridge, TN; Vinegar, Harold J [Bellaire, TX; John, Randy Carl [Houston, TX; Kim, Dong Sub [Sugar Land, TX

    2010-08-31

    High strength metal alloys are described herein. At least one composition of a metal alloy includes chromium, nickel, copper, manganese, silicon, niobium, tungsten and iron. System, methods, and heaters that include the high strength metal alloys are described herein. At least one heater system may include a canister at least partially made from material containing at least one of the metal alloys. At least one system for heating a subterranean formation may include a tubular that is at least partially made from a material containing at least one of the metal alloys.

  11. 3D structures of liquid-phase GaIn alloy embedded in PDMS with freeze casting.

    PubMed

    Fassler, Andrew; Majidi, Carmel

    2013-11-21

    Liquid phase electronic circuits are created by freeze casting gallium-indium (GaIn) alloys, such as eutectic gallium-indium (EGaIn), and encapsulating these frozen components within an elastomer. These metal alloys are liquid at room temperature, and can be cast using either injection or a vacuum to fill a PDMS mold and placing the mold in a freezer. Once solidified, a GaIn alloy segment can be manipulated, altered, or bonded to other circuit elements. A stretchable circuit can be fabricated by placing frozen components onto an elastomer substrate, which can be either patterned or flat, and sealing with an additional layer of elastomer. Circuits produced in this fashion are soft, stretchable, and can have complex 3D channel geometries. In contrast, current fabrication techniques, including needle injection, mask deposition, and microcontact printing, are limited to 2D planar designs. Additionally, freeze casting fabrication can create closed loops, multi-terminal circuits with branching features, and large area geometries. PMID:24067934

  12. Spark alloying of an AL9 alloy by hard alloys

    NASA Astrophysics Data System (ADS)

    Kuptsov, S. G.; Fominykh, M. V.; Mukhinov, D. V.; Magomedova, R. S.; Nikonenko, E. A.

    2015-08-01

    The phase compositions of spark coatings of Kh12M steel with a VT1-0 (titanium) alloy and T15K6 and T30K4 hard alloys are studied. It is shown that the TiC titanium carbide forms in all cases and tungsten carbide decomposes with the formation of tungsten in a coating. These processes are intensified by increasing time, capacitance, and frequency. The surface hardness, the sample weight, and the white layer thickness increase monotonically.

  13. Creep Resistant Zinc Alloy

    SciTech Connect

    Frank E. Goodwin

    2002-12-31

    This report covers the development of Hot Chamber Die Castable Zinc Alloys with High Creep Strengths. This project commenced in 2000, with the primary objective of developing a hot chamber zinc die-casting alloy, capable of satisfactory service at 140 C. The core objectives of the development program were to: (1) fill in missing alloy data areas and develop a more complete empirical model of the influence of alloy composition on creep strength and other selected properties, and (2) based on the results from this model, examine promising alloy composition areas, for further development and for meeting the property combination targets, with the view to designing an optimized alloy composition. The target properties identified by ILZRO for an improved creep resistant zinc die-casting alloy were identified as follows: (1) temperature capability of 1470 C; (2) creep stress of 31 MPa (4500 psi); (3) exposure time of 1000 hours; and (4) maximum creep elongation under these conditions of 1%. The project was broadly divided into three tasks: (1) Task 1--General and Modeling, covering Experimental design of a first batch of alloys, alloy preparation and characterization. (2) Task 2--Refinement and Optimization, covering Experimental design of a second batch of alloys. (3) Task 3--Creep Testing and Technology transfer, covering the finalization of testing and the transfer of technology to the Zinc industry should have at least one improved alloy result from this work.

  14. Single-Crystal NiAl-X Alloys Tested for Hot Corrosion

    NASA Technical Reports Server (NTRS)

    Nesbitt, James A.

    1999-01-01

    Single-crystal nickel aluminide (NiAl) has been investigated extensively throughout the last several years as a potential structural material in aero-gas turbine engines. The attractive features of NiAl in comparison to Ni-base superalloys include a higher melting point, lower density, higher thermal conductivity, and excellent oxidation resistance. However, NiAl suffers from a lack of ductility and fracture toughness at low temperatures and a low creep strength at high temperatures. Alloying additions of hafnium (Hf), gallium (Ga), titanium (Ti), and chromium (Cr) have each shown some benefit to the mechanical properties over that of the binary alloy. However, the collective effect of these alloying additions on the environmental resistance of NiAl-X was unclear. Hence, the present study was undertaken to examine the hot corrosion behavior of these alloys. A companion study examined the cyclic oxidation resistance of these alloys. Several single-crystal NiAl-X alloys (where X is Hf, Ti, Cr, or Ga) underwent hot corrosion testing in a Mach 0.3 burner rig at the NASA Lewis Research Center. Samples were tested for up to 300 1-hr cycles at a temperature of 900 C. It was found that increasing the Ti content from 1 to 5 at.% degraded the hot corrosion behavior. This decline in the behavior was reflected in high weight gains and large corrosion mound formation during testing (see the figures). However, the addition of 1 to 2 at.% Cr to alloys containing 4 to 5 at.% Ti appeared to greatly reduce the susceptibility of these alloys to hot corrosion attack and negated the deleterious effect of the increased Ti addition.

  15. The 13.9 GHz short pulse radar noise figure measurements utilizing silicon and gallium-arsenide mixer diodes

    NASA Technical Reports Server (NTRS)

    Dombrowski, M.

    1977-01-01

    An analysis was made on two commercially available silicon and gallium arsenide Schottky barrier diodes. These diodes were selected because of their particularly low noise figure in the frequency range of interest. The specified noise figure for the silicon and gallium arsenide diodes were 6.3 db and 5.3 db respectively when functioning as mixers in the 13.6 GHz region with optimum local oscillator drive.

  16. Lymphocytic interstitial pneumonitis: a cause of pulmonary gallium-67 uptake in a child with acquired immunodeficiency syndrome

    SciTech Connect

    Zuckier, L.S.; Ongseng, F.; Goldfarb, C.R.

    1988-05-01

    Lymphocytic interstitial pneumonitis (LIP) is currently recognized as a frequent pediatric manifestation of the acquired immunodeficiency syndrome (AIDS). We report the gallium scan findings in a 3-yr-old girl with this disorder and review its clinical, radiologic, and pathologic features. LIP must be a prime consideration in the differential diagnosis of diffuse pulmonary gallium uptake in pediatric AIDS patients. Further experience will afford greater perspective on the diagnostic role that nuclear medicine will ultimately play in this disease. 49 references.

  17. Effects of Organic Chelation on the Behavior of Aluminum Relative to Gallium During Pedogenesis

    NASA Astrophysics Data System (ADS)

    Herz, M. M.; Derry, L. A.

    2003-12-01

    This study of gallium and aluminum behavior in the soil weathering environment provides a first step toward using Ga/Al as a tracer of aluminum dynamics during pedogenesis. Previously, the interpretation of aluminum behavior in soils was confounded by the monoisotopic nature of aluminum and its subsequent lack of a comparative tracer. Like aluminum, gallium is a strongly hydrolyzing group III element. It is included in the same mineral systems as aluminum and the two are believed to have similar chemistries in most natural environments. Aluminum is a highly toxic metal whose removal from mineral matrices is enhanced by acid deposition and chelation by organic ligands. As much as 80% of dissolved aluminum in upper soil horizons can be complexed by organic ligands, most of which are secreted by plant and soil microorganisms to detoxify their surroundings. However, gallium makes comparatively unstable complexes with organic chelators, and is not expected to be carried into solution or leached from the soil profile by them to the same extent as aluminum. The Hawaiian Islands provide a unique opportunity to study the evolution of aluminum and gallium concentrations during soil development along gradients where age or climate varies, but all other soil forming factors are held constant. Ga/Al in older and more intensely weathered soils can be as high as 2.58 (mg/g), whereas the basaltic parent material is almost 10 times lower (0.30 mg/g). The factor driving soil Ga/Al ratios away from those found in parent material may be the strong control that organic chelation exerts over aluminum mobility. The enhancement of aluminum dissolution by organic chelation can be inferred from the decrease in Ga/Al ratios of exchangeable cations along a gradient of increasing rainfall; where wetter, more organic rich sites have Ga/Al ratios 10 to 100 times lower than drier sites where organic chelation is a less important factor in driving aluminum dynamics. Along this same gradient, the bulk soil shows an increase in Ga/Al despite an overall loss of both metals, indicating a relative enrichment of gallium in the secondary minerals. The results of preliminary laboratory syntheses of allophane minerals show that there is no significant fractionation of aluminum and gallium during secondary mineral formation in the absence of organic chelators.

  18. Chelator free gallium-68 radiolabelling of silica coated iron oxide nanorods via surface interactions

    NASA Astrophysics Data System (ADS)

    Burke, Benjamin P.; Baghdadi, Neazar; Kownacka, Alicja E.; Nigam, Shubhanchi; Clemente, Gonçalo S.; Al-Yassiry, Mustafa M.; Domarkas, Juozas; Lorch, Mark; Pickles, Martin; Gibbs, Peter; Tripier, Raphaël; Cawthorne, Christopher; Archibald, Stephen J.

    2015-09-01

    The commercial availability of combined magnetic resonance imaging (MRI)/positron emission tomography (PET) scanners for clinical use has increased demand for easily prepared agents which offer signal or contrast in both modalities. Herein we describe a new class of silica coated iron-oxide nanorods (NRs) coated with polyethylene glycol (PEG) and/or a tetraazamacrocyclic chelator (DO3A). Studies of the coated NRs validate their composition and confirm their properties as in vivo T2 MRI contrast agents. Radiolabelling studies with the positron emitting radioisotope gallium-68 (t1/2 = 68 min) demonstrate that, in the presence of the silica coating, the macrocyclic chelator was not required for preparation of highly stable radiometal-NR constructs. In vivo PET-CT and MR imaging studies show the expected high liver uptake of gallium-68 radiolabelled nanorods with no significant release of gallium-68 metal ions, validating our innovation to provide a novel simple method for labelling of iron oxide NRs with a radiometal in the absence of a chelating unit that can be used for high sensitivity liver imaging.The commercial availability of combined magnetic resonance imaging (MRI)/positron emission tomography (PET) scanners for clinical use has increased demand for easily prepared agents which offer signal or contrast in both modalities. Herein we describe a new class of silica coated iron-oxide nanorods (NRs) coated with polyethylene glycol (PEG) and/or a tetraazamacrocyclic chelator (DO3A). Studies of the coated NRs validate their composition and confirm their properties as in vivo T2 MRI contrast agents. Radiolabelling studies with the positron emitting radioisotope gallium-68 (t1/2 = 68 min) demonstrate that, in the presence of the silica coating, the macrocyclic chelator was not required for preparation of highly stable radiometal-NR constructs. In vivo PET-CT and MR imaging studies show the expected high liver uptake of gallium-68 radiolabelled nanorods with no significant release of gallium-68 metal ions, validating our innovation to provide a novel simple method for labelling of iron oxide NRs with a radiometal in the absence of a chelating unit that can be used for high sensitivity liver imaging. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr02753e

  19. Gallium-67 citrate imaging in head and neck tumors: report of cooperative group

    SciTech Connect

    Teates, C.D.; Preston, D.F.; Boyd, C.M.

    1980-07-01

    This report summarizes the experiences of the Oak Ridge Associated Universities Cooperative Group with the scanning of head and neck cancer using carrier-free gallium-67 citrate. Central nervous system and thyroid tumors and lymphomas were excluded. Fifty-six percent of primary head and neck tumors and their metastases were detected in 65 patients. The detection rates for primary and metastatic lesions were similar. Results of 1306 scans on patients with many types of cancer and suspicion of head and neck involvement indicate that a positive gallium scan was associated with tumor involvement five to nine times as often as no tumor, but a negative scan cannot reliably rule out involvement. In head and neck tumors, both primary and metastatic, lesions over 3 cm in diameter had a significantly higher detection rate than smaller lesions. Previous radiation or surgery did not affect accuracy.

  20. Origin of color centers in the flux-grown europium gallium garnet

    SciTech Connect

    Aleksandrovsky, A. S.; Arkhipkin, V. G.; Bezmaternykh, L. N.; Gudim, I. A.; Krylov, A. S.; Vagizov, F.

    2008-04-15

    Europium gallium garnet (EuGG) single crystals were grown from fluxes with various contents. Optical absorption spectra of EuGG grown from a flux containing calcium show an additional band in the ultraviolet and blue regions of the spectra as compared to the case of a calcium-free flux. Moessbauer spectra of the samples grown from the fluxes with different additives show no signs of other valence states of the europium ions except for 3+. However, they indicate changes in the crystal field due to the entrance of additive ions. The nature of the additional absorption must be the same as that for calcium-doped gadolinium gallium garnet, i.e., anion vacancies. Moessbauer isotope shifts and quadrupole splitting for EuGG are determined.

  1. Self-assembly of gold nanoparticles on gallium droplets: controlling charge transport through microscopic devices.

    PubMed

    Du, Kan; Glogowski, Elizabeth; Tuominen, Mark T; Emrick, Todd; Russell, Thomas P; Dinsmore, A D

    2013-11-01

    We describe the spontaneous assembly of ligand-stabilized gold nanoparticles on the surfaces of gallium droplets in suspension. By subsequent deposition of these coated droplets onto substrates with patterned electrodes, we form devices that have controlled architecture on the nanometer scale, which allows control of electron transport. In particular, we show that microscopic droplets can be brought into contact with one another with a monolayer of nanoparticles between them, resulting in a junction where electron transport is limited by the Coulomb blockade effect. We characterize the gallium surfaces by optical and electron microscopy and measurement of the interfacial tension. We measure the current-voltage characteristics of devices consisting of one or more Ga droplets and nanoparticle layers in series. The results agree well with the conventional theory of the Coulomb blockade and show how this approach could be used to form hierarchically structured electronic devices. PMID:24102520

  2. Proof-of-Concept Experiments on a Gallium-Based Ignitron for Pulsed Power Applications

    NASA Technical Reports Server (NTRS)

    Ali, H. K.; Hanson, V. S.; Polzin, K. A.; Pearson, J. B.

    2015-01-01

    Ignitrons are electrical switching devices that operate at switching times that are on the order of microseconds, can conduct high currents of thousands of amps, and are capable of holding off tens of thousands of volts between pulses. They consist of a liquid metal pool within an evacuated tube that serves both the cathode and the source of atoms and electrons for an arc discharge. Facing the liquid metal pool is an anode suspended above the cathode, with a smaller ignitor electrode tip located just above the surface of the cathode. The ignitron can be charged to significant voltages, with a potential difference of thousands of volts between anode and cathode. When an ignition pulse is delivered from the ignitor electrode to the cathode, a small amount of the liquid metal is vaporized and subsequently ionized, with the high voltage between the anode and cathode causing the gas to bridge the gap between the two electrodes. The electrons and ions move rapidly towards the anode and cathode, respectively, with the ions liberating still more atoms from the liquid metal cathode surface as a high-current plasma arc discharge is rapidly established. This arc continues in a self-sustaining fashion until the potential difference between the anode and cathode drops below some critical value. Ignitrons have been used in a variety of pulsed power applications, including the railroad industry, industrial chemical processing, and high-power arc welding. In addition, they might prove useful in terrestrial power grid applications, serving as high-current fault switches, quickly shunting dangerous high-current or high-voltage spikes safely to ground. The motivation for this work stemmed from the fact that high-power, high-reliability, pulsed power devices like the ignitron have been used for ground testing in-space pulsed electric thruster technologies, and the continued use of ignitrons could prove advantageous to the future development and testing of such thrusters. Previous ignitron designs have used mercury as the liquid metal cathode, owing to its presence as a liquid at room temperatures and a vapor pressure of 10 Pa (75 mtorr) at room temperature. While these are favorable properties, there are obvious environmental and personal safety concerns with the storage, handling, and use of mercury and its compounds. The purpose of the present work was to fabricate and test an ignitron that used as its cathode an alternate liquid metal that was safe to handle and store. To that end, an ignitron test article that used liquid gallium as the cathode material was developed and tested. Gallium is a metal that has a melting temperature of 29.76 C, which is slightly above room temperature, and a boiling point of over 2,300 C at atmospheric pressure. This property makes gallium the element with the largest relative difference between melting and boiling points. Gallium has a limited role in biology, and when ingested, it will be subsequently processed by the body and expelled rather than accumulating to toxic levels. The next section of this Technical Memorandum (TM) provides background information on the development of mercury-based ignitrons, which serves as the starting point for the development of the gallium-based variant. Afterwards, the experimental hardware and setup used in proof-of-concept testing of a basic gallium ignitron are presented. Experimental data, consisting of discharge voltage and current waveforms as well as high-speed imaging of the gallium arc discharge in the gallium ignitron test article, are presented to demonstrate the efficacy of the concept. Discussion of the data and suggestions on improvements for future iterations of the design are presented in the final two sections of this TM.

  3. Direct growth of graphene on gallium nitride using C2H2 as carbon source

    NASA Astrophysics Data System (ADS)

    Wang, Bing; Zhao, Yun; Yi, Xiao-Yan; Wang, Guo-Hong; Liu, Zhi-Qiang; Duan, Rui-Rei; Huang, Peng; Wang, Jun-Xi; Li, Jin-Min

    2016-04-01

    Growing graphene on gallium nitride (GaN) at temperatures greater than 900°C is a challenge that must be overcome to obtain high quality of GaN epi-layers. We successfully met this challenge using C2H2 as the carbon source. We demonstrated that graphene can be grown both on copper and directly on GaN epi-layers. The Raman spectra indicated that the graphene films were about 4-5 layers thick. Meanwhile, the effects of the growth temperature on the growth of the graphene films were systematically studied, and 830°C was found to be the optimum growth temperature. We successfully grew high-quality graphene films directly on gallium nitride.

  4. Chronic osteomyelitis: bone and gallium scan patterns associated with active disease

    SciTech Connect

    Tumeh, S.S.; Aliabadi, P.; Weissman, B.N.; McNeil, B.J.

    1986-03-01

    Bone and gallium scans are used to assess osteomyelitis patients with prior bone disease. To refine the criteria for interpreting these scans, the data from 136 consecutive patients with clinically suspected osteomyelitis were reviewed. Active osteomyelitis was diagnosed with surgery or biopsy and culture in 49 patients, excluded with the same criteria in 16, and excluded by clinical follow-up for at least 6 months in 71. Five different scintigraphic patterns were found. The true-positive and false-positive ratios, the likelihood ratios, and posterior probabilities for active osteomyelitis in each pattern were calculated. Only one pattern (gallium uptake exceeding bone-seeking radiopharmaceutical uptake) was indicative of active disease. Other patterns slightly raised or decreased the probability of disease. The extent of these changes varies directly with the prior probability of disease, determined from patient-specific factors (e.g., clinical data, laboratory data, findings on plain films) known best by the referring clinician.

  5. Electrodeposition of Ga-O Thin Films from Aqueous Gallium Sulfate Solutions

    NASA Astrophysics Data System (ADS)

    Vequizo, Junie Jhon M.; Ichimura, Masaya

    2013-07-01

    Ga-O based thin films were electrodeposited on fluorine-doped tin oxide (FTO)-coated glass substrate at room temperature from aqueous gallium sulfate solution with hydrogen peroxide (H2O2). Effects of different deposition parameters such as deposition voltage, amount of H2O2 and deposition time were investigated and presented. Nearly smooth and crack-free morphologies were attained at -1.0 V vs SCE deposition potential. As-deposited films showed O to Ga ratio of 2.0, which signified GaOOH formation. Thermal annealing of the as-deposited films in ambient air at 500-600 °C reduced the O/Ga ratio closer to stoichiometric gallium oxide (Ga2O3) and retained the morphology of Ga-O thin films. As-prepared films with ˜0.2 µm thickness had 80% transparency in the visible wavelength range.

  6. Anomalous Magneto-Optical Behavior of Rare Earth Doped Gallium Nitride

    NASA Astrophysics Data System (ADS)

    Helbers, Andrew; Mitchell, Brandon; Woodward, Nathaniel; Dierolf, Volkmar

    We have observed unusual magneto-optical properties in rare earth doped gallium nitride. Specifically, the reversal of a magnetic field applied parallel to the c-axis produces unexpected, marked differences in luminescence spectra in several of our samples. Notably, relative emission strengths of Zeeman-split lines from the rare earth ions appear to change when the field is reversed. These effects were not observed in rare earth doped lithium niobate and lithium tantalate, which are also hexagonal and polar. Measurements for erbium doped gallium nitride suggest that these asymmetries seem to be linked to the degree of ferromagnetism of the samples. Results are presented showing these differences. The symmetry of the observed effects requires a perturbation of the RE states with a screw like symmetry. We explore whether this may be accomplished by defects such as threading dislocations. The work related to ferroelectric materials was supported by NSF Grant (DMR-1008075).

  7. P-doping mechanisms in catalyst-free gallium arsenide nanowires.

    PubMed

    Dufouleur, Joseph; Colombo, Carlo; Garma, Tonko; Ketterer, Bernt; Uccelli, Emanuele; Nicotra, Marco; Fontcuberta i Morral, Anna

    2010-05-12

    Doped catalyst-free GaAs nanowires have been grown by molecular beam epitaxy with the gallium-assisted method. The spatial dependence of the dopant concentration and resistivity have been measured by Raman spectroscopy and four point electrical measurements. Along with theoretical considerations, the doping mechanisms have been revealed. Two competing mechanisms have been revealed: dopant incorporation from the side facets and from the gallium droplet. In the latter incorporation path, doping compensation seems to play an important role in the effective dopant concentration. Hole concentrations of at least 2.4 x 10(18) cm(-3) have been achieved, which to our knowledge is the largest p doping range obtained up to date. This work opens the avenue for the use of doped GaAs nanowires in advanced applications and in mesoscopic physics experiments. PMID:20373777

  8. Antitumor Activity and Toxicity of Salts of Inorganic Group IIIa Metals: Aluminum, Gallium, Indium, and Thallium

    PubMed Central

    Hart, Michael M.; Adamson, Richard H.

    1971-01-01

    The toxicity and antitumor activity of salts of the Group IIIa metals aluminum, gallium, indium, and thallium were determined. With the (lethal dose)50 as a measure, the decreasing order of toxicity was TlCl3 ≥ In(NO3)3 > Ga(NO3)3 > Al(NO3)3. All four metals exhibited antitumor activity, but when the tumor was inoculated by a route different from that of the drug, only Ga+3 and, to a lesser extent, In+3 inhibited tumor growth. Ga(NO3)3 was found to inhibit the growth of three out of four rodent solid tumors. Gallium therefore has potential therapeutic usefulness for treatment of solid tumors in man. PMID:5283954

  9. Thermodynamic property evaluation and magnetic refrigeration cycle analysis for gadolinium gallium garnet

    SciTech Connect

    Murphy, R.W.

    1994-12-01

    Based on relevant material property data and previous model formulations, a magnetothermodynamic property map for gadolinium gallium garnet (Gd{sub 3}Ga{sub 5}O{sub 12}) was adapted for refrigeration cycle analysis in the temperature range 4-40 K and the magnetic field range 0-6 T. Employing methods similar to those previously developed for other materials and temperature ranges, assessments of limitations and relative performance were made for Carnot, ideal regenerative, and pseudo-constant field regenerative cycles. It was found that although Carnot cycle limitations on available temperature lift for gadolinium gallium garnet are not as severe as the limitations for materials previously examined, considerable improvement in cooling capacity and temperature lift combinations can be achieved by using regenerative cycles if serious loss mechanisms are avoided.

  10. Growth of epitaxial iron nitride ultrathin film on zinc-blende gallium nitride

    SciTech Connect

    Pak, J.; Lin, W.; Wang, K.; Chinchore, A.; Shi, M.; Ingram, D. C.; Smith, A. R.; Sun, K.; Lucy, J. M.; Hauser, A. J.; Yang, F. Y.

    2010-07-15

    The authors report the growth of iron nitride on zinc-blende gallium nitride using molecular beam epitaxy. First, zinc-blende GaN is grown on a magnesium oxide substrate having (001) orientation; second, an ultrathin layer of FeN is grown on top of the GaN layer. In situ reflection high-energy electron diffraction is used to monitor the surface during growth, and a well-defined epitaxial relationship is observed. Cross-sectional transmission electron microscopy is used to reveal the epitaxial continuity at the gallium nitride-iron nitride interface. Surface morphology of the iron nitride, similar to yet different from that of the GaN substrate, can be described as plateau valley. The FeN chemical stoichiometry is probed using both bulk and surface sensitive methods, and the magnetic properties of the sample are revealed.

  11. Osteomyelitis and infarction in sickle cell hemoglobinopathies: differentiation by combined technetium and gallium scintigraphy

    SciTech Connect

    Amundsen, T.R.; Siegel, M.J.; Siegel, B.A.

    1984-12-01

    Clinical records and scintigrams were reviewed of 18 patients with sickle cell hemoglobinophaties who had undergone combined technetium and gallium scintigraphy during 22 separate episodes of suspected osseous infection. The combined scintigrams were correctly interpreted as indicating osteomyelitis in four studies. Of 18 studies in patients with infarction, the combined scintigrams were correctly interpreted in 16 and showed either no local accumulation of Ga-67 or less accumulation than that of Tc-99m MDP at symptomatic sites. In the other two studies, the scintigrams were falsely interpreted as indicating osteomyelitis and showed congruent, increased accumulation of both Tc-99, MDP and Ga-67. This pattern must be considered indeterminate. Overall, the results indicate that the combination of technetium and gallium scintigraphy is an effective means to distinguish osteomyelitis from infarction in patients with sickle cell hemoglobinopathies.

  12. Magnetic refrigeration cycle analysis using selected thermodynamic property characterizations for gadolinium gallium garnet

    SciTech Connect

    Murphy, R.W. )

    1992-02-10

    Magneto-thermodynamic property characterizations were selected, adapted, and compared to material property data for gadolinium gallium garnet in the temperature range 4--40 K and magnetic field range 0--6 T. The most appropriate formulations were incorporated into a model in which methods similar to those previously developed for other materials and temperature ranges were used to make limitation and relative performance assessments of Carnot, ideal regenerative, and pseudo-constant field regenerative cycles. Analysis showed that although Carnot cycle limitations on available temperature lift for gadolinium gallium garnet are not as severe as those for materials previously examined, substantial improvements in cooling capacity/temperature lift combinations can be achieved using regenerative cycles within specified fields limits if significant loss mechanisms are mitigated.

  13. Magnetic refrigeration cycle analysis using selected thermodynamic property characterizations for gadolinium gallium garnet

    SciTech Connect

    Murphy, R.W.

    1992-09-01

    Magneto-thermodynamic property characterizations were selected, adapted, and compared to material property data for gadolinium gallium garnet in the temperature range 4--40 K and magnetic field range 0--6 T. The most appropriate formulations were incorporated into a model in which methods similar to those previously developed for other materials and temperature ranges were used to make limitation and relative performance assessments of Carnot, ideal regenerative, and pseudo-constant field regenerative cycles. Analysis showed that although Carnot cycle limitations on available temperature lift for gadolinium gallium garnet are not as severe as those for materials previously examined, substantial improvements in cooling capacity/temperature lift combinations can be achieved using regenerative cycles within specified field limits if significant loss mechanisms are mitigated.

  14. 8-Quinolinolato Gallium Complexes: Iso-selective Initiators for rac-Lactide Polymerization

    PubMed Central

    2013-01-01

    The synthesis and characterization of a series of 8-quinolinolato gallium complexes is presented, and the complexes are analogous to a series of aluminum complexes previously reported. The complexes have been shown to be active initiators for the ring-opening polymerization of rac-lactide. High degrees of polymerization control are demonstrated, as exemplified by the linear evolution of molecular weight as the polymerization progresses, narrow polydispersity indices, and molecular weights corresponding to those predicted on the basis of initiator concentration. Some of the initiators show iso-selective polymerization of rac-lactide, with Pi = 0.70. The polymerization rates have been monitored, and the pseudo first-order rate constants are compared to those of analogous aluminum compounds. The 8-quinolinolato gallium initiators show rates approximately 3 times higher than those of the series of aluminum compounds, while maintaining equivalently high iso-selectivity (Pi = 0.70) and polymerization control. PMID:24138079

  15. Carbon doping of gallium arsenide and reflectance difference spectroscopy of compound semiconductors grown by metalorganic vapor-phase epitaxy

    NASA Astrophysics Data System (ADS)

    Begarney, Michael John

    The surface structure and chemistry of compound semiconductors used in heterojunction bipolar transistors was investigated. Lattice-matched, single crystal films of gallium arsenide and indium phosphide were deposited by metalorganic vapor-phase epitaxy in a horizontal-flow, quartz reactor. Two areas of the transistor fabrication process were studied: (1) carbon doping of the gallium arsenide base layer using carbon tetrachloride, and (2) in-situ monitoring of the surface reconstructions of gallium arsenide and indium phosphide by reflectance difference spectroscopy for improved heterointerface formation. Carbon tetrachloride was found to effect the growth of gallium arsenide in two ways: (1) reaction of chlorine with adsorbed gallium atoms to produce volatile GaCl, and (2) reaction of chlorine with the GaAs film to produce GaCl3. The latter of these reactions was found to be insignificant below a temperature-dependent threshold ratio of chlorine to gallium. At lower values of this ratio, step bunching and pinning was observed, while at higher values, pits ranging from 20 to 50 nm in diameter resulted. We show that these results arise due to the presence of the c(4 x 4) gallium arsenide reconstruction during crystal growth, and the site-specific adsorption of CCl4 at gallium atom sites, which are present only at step edges for this reconstruction. The relationship between the reflectance difference spectra and the atomic structure of arsenic-rich reconstructions of GaAs (001) were investigated. It was found that a roughening process, involving the desorption of arsenic and outdiffusion of gallium atoms to the surface, takes place as the surface structure changes with decreasing arsenic coverage. We determined that the intensity of the negative peak at 2.8 eV strongly depends on the presence of adsorbed alkyl groups and gallium atoms, while, by contrast, the intensity of the positive peak at 2.9 eV is directly proportional to the density of (2 x 4)-type dimers. We determined that the reflectance difference spectra of InP (001) surfaces with phosphorous coverages ranging from 1.0 to 0.25 result from linear combinations of the line shapes of the uniformly reconstructed (2 x 1) and (2 x 4) surfaces. A linear relationship was found between the coverage of each phase and the weighting factor in the generated spectra.

  16. Catalyst Alloys Processing

    NASA Astrophysics Data System (ADS)

    Tan, Xincai

    2014-10-01

    Catalysts are one of the key materials used for diamond formation at high pressures. Several such catalyst products have been developed and applied in China and around the world. The catalyst alloy most widely used in China is Ni70Mn25Co5 developed at Changsha Research Institute of Mining and Metallurgy. In this article, detailed techniques for manufacturing such a typical catalyst alloy will be reviewed. The characteristics of the alloy will be described. Detailed processing of the alloy will be presented, including remelting and casting, hot rolling, annealing, surface treatment, cold rolling, blanking, finishing, packaging, and waste treatment. An example use of the catalyst alloy will also be given. Industrial experience shows that for the catalyst alloy products, a vacuum induction remelt furnace can be used for remelting, a metal mold can be used for casting, hot and cold rolling can be used for forming, and acid pickling can be used for metal surface cleaning.

  17. Investigation of spin transport and accumulation in aluminum gallium arsenide

    NASA Astrophysics Data System (ADS)

    Misuraca, Jennifer

    This dissertation describes spin injection, transport, and detection experiments from Fe electrodes into a bulk AlGaAs channel. This semiconducting alloy is one of a class of persistent photoconductors, chosen as the spin transport medium because its carrier density can be tuned in a controlled manner via photoexcitation through the metal to insulator transition (MIT) in situ. This allows one to determine the dependence of spin lifetime on a variety of external parameters including carrier density, all on one sample. This research represents the first electrical spin-dependent measurements in this material and describes the dependence of the Hanle signal size and spin lifetime on bias, temperature, and carrier density. The photoexcitation needed to change the carrier density in this material comes from an infrared light-emitting diode (IR LED). The first step of this project was to characterize the new, highly Si doped Al0.3Ga 0.7As heterostructures, in order to determine how the illumination of the sample will affect the parameters of the material. To complete this study, Hall crosses were fabricated from the AlGaAs material and the transport properties were measured between 350 mK and 165 K. The resistivity, carrier density, and mobility were determined as a function of temperature for a variety of different illumination times. From this data, the MIT, scattering mechanisms, and the shape of the band tail of the density of states (DOS) were investigated. In fact, this is the first work to electrically probe the DOS in AlGaAs. Once the materials were characterized, they were used to fabricate lateral spin transport devices. Spin transport and accumulation were studied in detail via Hanle effect measurements, which measure the dephasing of electron spins in a perpendicular magnetic field. From these measurements, the spin lifetime of the material can be calculated, and is in the nanosecond range for all measured carrier densities. The spin lifetimes are measured using three distinct measurement configurations which all give consistent results. The dependence of spin lifetime and Hanle signal size are reported as a function of bias, temperature, and carrier density. This is the first spin transport experiment using a persistently photoconductive material as the spin transport channel in order to change the carrier density of the material in situ. The research in this dissertation successfully provides a framework for the continuation of spin injection and detection studies in this and other alloy semiconductors, and provides insight into how the spin lifetime depends on the doping levels in semiconductors.

  18. Gallium scintigraphy demonstration of an appendiceal mucocele: a proposed mechanism of uptake.

    PubMed

    Alpert, L; Friedman, R

    1981-08-01

    An appendiceal mucocele demonstrated intense early avidity for Ga-67, despite the lack of inflammatory cells to account for the uptake. It is proposed that the acid mucopolysaccharide component of the mucus within the lumen and lining cells accounted for the uptake of the gallium ion, in a similar manner to the uptake of its analogue, the ferric ion, as demonstrated by intense staining of mucus by the colloidal iron technique. PMID:6167393

  19. Gallium scintigraphy demonstration of an appendiceal mucocele: a proposed mechanism of uptake

    SciTech Connect

    Alpert, L.; Friedman, R.

    1981-08-01

    An appendiceal mucocele demonstrated intense early avidity for Ga-67, despite the lack of inflammatory cells to account for the uptake. It is proposed that the acid mucopolysaccharide component of the mucus within the lumen and lining cells accounted for the uptake of the gallium ion, in a similar manner to the uptake of its analogue, the ferric ion, as demonstrated by intense staining of mucus by the colloidal iron technique.

  20. An advanced space photovoltaic concentrator array using Fresnel lenses, gallium arsenide cells, and prismatic cell covers

    NASA Technical Reports Server (NTRS)

    O'Neill, Mark J.; Piszczor, Michael F.

    1988-01-01

    The current status of a space concentrator array which uses refractive optics, gallium arsenide cells, and prismatic cell covers to achieve excellent performance at a very low array mass is documented. The prismatically covered cells have established records for space cell performance (24.2 percent efficient at 100 AM0 suns and 25 C) and terrestrial single-junction cell performance (29.3 percent efficient at 200 AM1.5 suns and 25 C).